Much as above. I start Kleo and I get the icon on the taskbar for a second then it is gone and that is it?
Any tips?

I resolved the issue, but there is something funny in the background.
There was a Kleopatra process which I had to kill and restart. It seems this resolves the issue.

My apologies if this is late to the party. I'm running Kubuntu 18.04. Did an exhaustive search for any problems or solutions and came up empty. So just started blindly searching the net for anything KDE related to Kleopatra not launching.

Michael, Your solution solved my problem, but I am still wondering why this happened in the first place. But at least I now know to launch htop, find kleo, F9 (kill) it and then it launches.

If for some unforeseen reason you or anyone else stumbles upon this thread and has a solution or anything to add to the discussion would be greatly appreciated.

Thanks for reading