At some point while monitoring, the tool stops with an error:
A network-related or instance-specific error occurred while establishing a connection to SQL Server. The server was not found or was not accessible. Verify that the instance name is correct and that SQL Server is configured to allow remote connections. (provider: Named Pipes Provider, error: 40 - Could not open a connection to SQL Server)
Is there a way to tell when that error occurred?
You can use the log viewer to open the relevant log file to look for the error:
The application is logged by TracerX.
The log viewer "TracerX-Viewer.exe" is located in the folder "C:\Program Files\Idera\SQL Check\" or "C:\Program Files (x86)\Idera\SQL Check\".
The log files are located in the folder "C:\Users\<your_user_name>\AppData\Local\Idera\SQL Check\Logs\". The "AppData" folder may (or may not) be hidden by Windows.