Linux Mint 19.3 and Libreoffice 6.4.0.3. Also running Compiz. This has been working great, but now, If I try and create a new label using mailmerge from a spreadsheet, the config screen comes up, I select the label format and when I press “New Document”, I get a blank page, all black, no Libreoffice Header or menus. Doing anything to that window reduces it to a dot on the screen. I can and Maximize or close but still no functional window.
I should add. I have a laptop running all the same software and versions, and it works fine. Compiz and all.
Have your tried the same thing in Safe Mode of LibreOffice (Help -> Restart in Safe Mode...)?