If you are using the latest VisualGDB version, something is likely interfering with the VisualGDB internals. Please make sure you use an unmodified VisualGDB installation. If the problem persists, please try installing it on a different computer.
Found some dependency on the presence of CustomTargetProviders (TelnetTarget) in the project, even if this provider is not currently used (deploy and debug occurs via ssh on main build machine). If the solution is reopened and the debug test is performed first only for the project with ssh, then debugging works
This could explain it. If the custom target provider would cause the test host process to crash unexpectedly, VisualGDB would indeed display this message.
Our best advice would be to try attaching to the TestHost.exe executable and checking for exceptions. You can also try showing a message box with the current PID from the constructor of your target provider to make attaching easier.