Chiming in on this one
On Illustrator 27.3.1
Windows 11 - 22621.1413
Fontself version 3.5.8 (55c89)
Loading indicator (Greyed out background in entire panel, spinning loading circle) stuck on loading forever. Only active part of Fontself from there is hamburger menu, where pressing reload application breaks the loading but deletes unsaved data, and pressing check for updates breaks loading error, and keeps all unsaved data.
Have tried with lineart, expanded shapes (several grouped) and expanded shapes joined with pathfinder, expanded shapes in isolation mode, compound shapes… Everything seems to break it?
Sometimes selecting the shape with A works, sometimes selecting with V tool works, but nothing consistent yet.
When it does work, it works just fine, but this is frustrating to work with as it is now.
Have tried different solutions from different threads in this forum, and ended up reinstalling, only to have the same error.
Hope it gets fixed soon.