the nextcloud icon sits on the tray but no window is visibel. it is listed in the background aps.
how do I make the hidden window visiblle?
I suspect that the old config of nextcloud caused the problem.
I had a similar problem after upgrading nextcloud flatpak from 3.x to 4.x.
The sync process was running but no window appeared.
After I removed old configs (everything under ~/.var/app/com.nextcloud.desktopclient.nextcloud), the nextcloud then ran normally.
Of course I had to reconfigure nextcloud and resync everything after nuking my old configs.