open dolphin right click a folder select "Compress to..." in Ark dialog, select 7zip type, enter a file name, click "ok" button Two problems occur randomly on my system... Sometimes ark shows a notification about finished compression but no file appears in destination folder (???). Sometimes nothing happens when I click "ok" to start the compression.
Were you able to find any specifics, some common ground? 20+ tests archiving like that to a new .7z file and also to already existing ones. This issue doesn't occur in my system (Neon 5.12).
Does not fault on my system try to download and reinstall 7zip Kubuntu 18.04 KDE Plasma Version 5.12.6 KDE Frameworks Version 5.44.0 Qt Version 5.9.5
Closing for now. Please reopen if you figure out how to reproduce the issue.