I have been running the appimages without problem thru end of June.
None of the July appimages I have tried will run.
Reverting to an end of June version works again.

Is this a known issue and can you provide a link to the last working version?

When will this be corrected?

I know this isn't much help, but you're not the only one. I don't have any trouble with Appimages on Linuxmint Cinnamon or xfce. They run as they're supposed to after give the file permissions to be executable. But I'm new to KDE Plasma. I downloaded two different app images for two different programs today. Neither one will work. Then I tried downloading a helper program, but it as an AppImage too. Of course, it didn't work either.

Mounting Google Drive to Dolphin turned into a nightmare as well. The only way I could come half-way to making it work was using Rclone with it.

My problem was specifically with the KMyMoney appimage. I incorrectly posted to the general kde forum. When I reposted it to the KMyMoney forum, the developer quickly found the problem with the appimage and reissued working versions.