Hi Nikos,
I had a different issue after trying to install and use Fontself on a brand new pc with Windows 11 on in Greece.
Here was my issue: Blank Screen on Windows 11 - #3 by michalis
I also tried all the troubleshooting steps that were indicated here but nothing fixed the issue.
Furthermore, I sent the log files to Fontself support but they were unable to locate any problems and resolve them.
Since I have seen a few more users here in Greece and in Europe facing (not the exact same but) similar bugs, I wonder if there’s an issue that has to do with the location and certain restrictions.
Sadly though, the answer I kept receiving from Fontself is that there’s a problem with my pc and that I should uninstall it and request a refund (which was not my objective).
As a last resort, I contacted tech support for my pc but they didn’t find something problematic in the pc’s settings that wouldn’t allow the extension to function properly.
The point is that, at the end of the day, I still cannot use Fontself as well.
Personally, I will be waiting for an update on Fontself’s part for the next few weeks.
If that does not happen, then I will have to request a refund indeed I guess.
Kind regards