The debug output is
[2560] org.kde.pim.kleopatra: Checking Ui Server connectivity... [2560] UI server not running, starting it [2560] org.kde.pim.kleopatra: UiServer: client connect on fd 1528 [2560] org.kde.pim.kleopatra: UiServer: nonce check failed [2560] org.kde.pim.libkleopatraclientcore: Could not find "kleopatra" in PATH.
which means that libkleopatraclientcore couldn't start kleopatra, but at the same time the UiServer seems to be running? Okay, maybe the lines are in wrong order and the connect doesn't fail because the server isn't running but because of the wrong nonce.