Never heard of such an issue.
It seems you install with the admin installer as the pyrevit-master folder is in program files
you install points to a default extensions path to your appdata folder
your pyrevit-config.ini does not state anything related to extensions
- do you have some remaining of previous install in your %appdata%/pyrevit or %appdata%/pyrevit-master ?
- edit your config file with your path to the custom extension set in this manner:
[core]
userextensions = ["C:\\pathtoyourextensions"]