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Troubleshooting Viscosity Problems (Windows)

In rare instances Viscosity, or one of its components, may encounter a problem that prevents it from being able to function correctly under Windows. Below you can find some solutions to the more common issues you might face. Most issues relating to the driver, network adapter or service on Windows are generally caused by Antivirus or Network Security software. We recommend to disable any such software when following this guide.

If the problem you are encountering is not listed here, please check the Troubleshooting Connection Problems article for common connection problems and solutions for them.

Background Service Not Running When Updating to Version 1.10.6

Viscosity 1.10.6 (and later) require .NET 4.8.1 runtime. In most instances this should have already been automatically installed in the past by Windows Update. But if it hasn’t, the Viscosity updater will automatically detect this and download and run the .NET 4.8.1 updater.

After the .NET update is installed, the .NET updater will instruct you to reboot your computer and re-run the Viscosity update. If the computer isn't rebooted, or the Viscosity updater isn't re-run, you'll likely receive a "Background Service Not Running" error when attempting to connect to your VPN connections. If this applies to you, it can be resolved by rebooting your computer (if you haven't already), and then re-running the Viscosity updater. You can re-run it by opening Viscosity, going to the Viscosity menu and selecting Settings, clicking on the General icon, and then clicking the "Check Now" button.

If you are an IT administrator and your users are running into this issue, it's recommended you deploy the .NET 4.8.1 prior to updating Viscosity. The .NET update can be downloaded from the Microsoft website.

Please note that this information only applies when updating from an older version of Viscosity (1.10.5 or older) to the latest version. If you are encountering a "Background Service Not Running" error for a different reason, or are still encountering it after following the above steps, please refer to the section below.

Background Service Not Running

If you continue to see this message when trying to connect and you have been able to successfully connect in the past, first simply try to restart your PC to release any blocks or locks on your computer. Before you do this though, if you run any Antivirus or Network Security software, add an exception for the following files:

  • C:\Program Files\Viscosity\Viscosity.exe
  • C:\Program Files\Viscosity\ViscosityService.exe

If after a reboot you continue to see this message, you may need to reinstall the service. To do so:

  1. Disable any Antivirus or Network Security Software
  2. Download the latest version of the Viscosity Installer here
  3. Run the installer and follow the installation instructions
  4. Start Viscosity and attempt to connect again

If after following these instructions you continue to see this problem, the most likely cause is another application is either blocking the service, the service connection, or has quarantined the service. The easiest way to resolve this is an uninstall/reinstall. Please try the following:

  1. Add an exception to any Antivirus or Network Security software you run for Viscosity following the instructions above if you have not already
  2. Uninstall Viscosity by following these instructions. You do not need to remove your connections and settings.
  3. Restart your PC (it is important this is actually done to release any locks in Windows)
  4. Download the latest version of the Viscosity Installer here
  5. Run the installer and follow the installation instructions
  6. Start Viscosity and attempt to connect again

Adapter Creation Failed or Adapters appearing as Unknown Devices

You may have received an error from Viscosity like 'Windows is reporting a problem with Viscosity's network interface. Status: 37'. This error generally occurs when the Viscosity driver has not been installed correctly, for example has been blocked by AV or security software, or has become damaged or corrupt by another application. To remedy this:

  1. Right click the Start Button and select Device Manager
  2. Expand Network Adapters
  3. Right click any Viscosity Virtual devices, or Unknown Devices, and click Uninstall device
  4. At the prompt, tick Delete the device driver software for this device.
  5. Uninstall Viscosity, keep your settings and connections.
  6. Cold boot your PC. This means shut your PC down by right clicking the Start button, going to Shut down or sign out, and selecting Shut down (or Shut down and Update).
  7. Once shutdown, start your computer up again.

Once you are back in Windows:

  1. Download the latest version of the Viscosity Installer here.
  2. Disable any AV or security software.
  3. Run the installer.
  4. Continue with the installation.
  5. Attempt to connect again.

A full list of device error codes can be found via Microsoft here.

Large Number of Adapters Present

If you have a lot of connections, or import a lot of connections, you may find a large number of Viscosity adapters being created. While this will generally have no impact on the performance of your PC, some users prefer for this not to happen. The simplest fix is to use Single Adapter Mode (Windows).

The easiest way to remove the unwanted adapters is to simply Uninstall Viscosity, ensuring that you don't remove your connections and settings, and then Install Viscosity again.

If you don't want to use Single Adapter mode, for example because you want to use multiple connections at the same time, but want to have a lot of connections imported, ensure "Create VPN network adapter on import" is not ticked in Preferences -> Advanced. This way an adapter will not be created until you use a connection for the first time.

CreateFile failed on TAP device

Please see the Adapters appearing as Unknown Devices section above.

Viscosity Does Not Start

If you start Viscosity and the system tray icon does not appear, or Viscosity closes immediately, this is generally caused by Antivirus software falsely blocking Viscosity. To relieve this issue, most Antivirus software allows you to add an exception for software. We recommend you add an exception for Viscosity.exe, ViscosityService.exe and openvpn.exe, these are generally located at C:\Program Files\Viscosity unless you installed Viscosity in a different location.

We also recommend you request your Antivirus provider to white list Viscosity, most Antivirus software providers have a section on their website to do this.

Exitcode -1073741701 or Error Code 0xc000007b

OpenVPN may display an exit code in the log of -1073741701 or 0xc000007b, tapinstall.exe may fail when installing Viscosity, or some Viscosity components may display an error with one of these error codes. This is usually caused by the Visual C++ Redistributable installation being missing or damaged. On ARM64 computers this is typically caused by other software replacing the Visual C++ Redistributable for the wrong architecture (for example Microsoft Office has mistakenly done this in the past).

Visual C++ Redistributable issues can usually be resolved by following the steps below:

  1. Download the latest version of the Microsoft Visual C++ Redistributable from the Microsoft download page. Please select the architecture matching your machine when downloading. For ARM64 machines this should be the install listed under X64 (which is dual architecture) rather than the ARM64-only version.
  2. Run the downloaded installer (it should be in your Downloads folder). If the latest version of the redistributable isn’t already installed, let it go through the installation process and then run the installer again. You should then see a “Modify Setup” window. Click the “Uninstall” button and follow the steps.
  3. Run the installer again and let it re-install the redistributable.
  4. Run the installer again. From the “Modify Setup” window click on the “Repair” button and follow the steps.
  5. Download the latest version of Viscosity from our website and run the installer.

Tapinstall.exe Application Error

If you see a "tapinstall.exe - Application Error" message when trying to install or uninstall Viscosity, please refer to the troubleshooting steps in the section above.

Viscosity Crashes with FailFast Error

Viscosity may crash immediately on start, with the following error in the crash report:

The application requested process termination through System.Environment.FailFast

This usually means an application on your PC is trying to hook itself into Viscosity, most likely a development application. Please ensure applications for debugging, and intrusive anti-virus applications, have rules that do not try to block or debug Viscosity or it will not function.

It could also mean your system files are damaged. Try running the .NET repair tool or restoring Windows from Settings -> Update & Security -> Recovery.