Please include the flowing when reporting a bug:
Mac version Sonoma 14.6.1
Downloaded Fontbase 5 days ago
Updated my mac yesterday and now Fontbase wont respond! Tried restarting my mac and all that but still nothing:( Can you help me?
Hello @pernillere, thank you for your post and welcome to the forum 
Have you perhaps already tried to re-install FontBase after the OS update?
Resetting FontBase settings can also be an option under the current circumstances.
Thank you again,
Yuriy
FontBase Dev Team
I think I know the problem and solution to this.
The Fontbase app doesn’t behave like other “normal” apps (like say Apple Reminders as an example), where you can open the app window by clicking on the Dock icon, and close the app window with command-W or the top-left red dot button, and keep the app active in the background. In fact, it doesn’t even seem to use the native top-left close, minimize, maximize buttons if you look closely.
It seems that in an update at some point there might have been a change, and there’s now a menubar icon that needs to be clicked for the Fontbase window to show.
It seems that you can open/start Fontbase by clicking on the icon in the Dock, and it starts running in the background (see in Activity Monitor), but shows no window, or dot under its Dock icon to indicate it is running. Only when you further click on the menubar icon does it show its window and Dock icon active dot.
My guess is Fontbase was made in some legacy non-standard way, and that results in these sorts of obscure issues as macOS evolves and different scenarios aren’t covered by the way Fontbase’s UI has been created originally.
Still happy it’s the best value app for this kind of thing, and hope it gets more TLC in improving, especially now we have things like Cursor and Claude for AI coding and improvement.
To add to this, it could be the “Start hidden” Setting is the issue, and only those that enabled that setting are having this issue.