The scripted and automated installation of SQL Express 2017 as part of the trial and POC installation package for Goliath Performance Monitor may fail when utilized on non-English versions of Windows.
The work-around is to install the SQL Express Instance manually.
To do this, navigate to the installation folder for Goliath Performance Monitor, by default, this is:
C:\Program Files (x86)\MonitorIT
You will see an MSINSTALLS folder that has the SQL Server Express 2017 installer. Run this manually, accepting the defaults. For full instructions please see this related article.
After installation, try re-launching the GPM console.