TransitPackage Handler - Access to the path... denied


I have just downloaded and installed the TransitPackage Handler

But when I click on "Open StarTransitPackage" in Studio 2019 or 2017 (both most recent builds), I get this error message:

"Access to the path 'C:\Users\[username]\StarTransit\f3f81c7f-098b-4c31-8b77-c891e83aab5e' is denied."

I have also tested it on different machines, even made a Studio reset/Freshstart and installed the app on a fresh VM with a new Studio 2019 installation (no other apps installed) - same result.

The strange thing is that during installation, the app indeed seems to create a "StarTransit" folder which is not what I would expect.

Any hints how to solve this?