On my Ubuntu 24.04 LTS, I was using AppImageLauncher to help mange my AppImage files. Recently I've tried to add three different AppImage files. All three failed to run.
I did what I usually do; download the AppImage file, right clicked on it and checked the Allow Executing File As Program box. Usually you could then double click on the AppImage file and it would launch AppImageLauncher which would offer to "Integrate" the AppImage file or just "Run It Once". Well that's the part that stopped working. AppImageLauncher would error out on both the Run and Integrate options which would keep your AppImage file from starting. The solution is to just uninstall AppImageLauncher.
To do this, simple open a terminal window and type the follow line:
sudo apt purge appimagelauncher