[DragoLord19d]

Originally Posted by kovidgoyal

There should be no Qt issues between 4.10 and 4.11. This will be because the window is opening offscreen, probably because you recently
connected a secondary monitor or tv or similar. You can bring the window back onscreen
by using the technique described here:
https://www.technipages.com/bring-of...ck-onto-screen

Originally Posted by BetterRed

"Missing' secondary monitor is but one trigger for the main calibre window not appearing. But in recent times there have several of instances of calibre windows 'going off screen'.

Until recently I would have said it was limited to secondary (dialogue) windows, but last week someone had the problem with the Viewer not appearing. The solution has been to use the 'Fix 3' option in the link Kovid provided. You should try it in this case -- if you haven't already done so.

BR

I have tried it, no joy.