Debugging an AppImage that does not launch

The Panwriter AppImage hangs without error when launched. When launched from the command line (with option --no-sandbox), the last thing reported is:

Checking for update
Update for version 0.8.4 is not available (latest version: 0.8.4, downgrade is disallowed).
checkForUpdatesAndNotify called, downloadPromise is null

It did launch as expected the first time, when I integrated it using AppImageLauncher’s ‘Integrate and run’ button. Apparently the cause of the hang is skipped when running immediately after integration. The update check reported above might be where the problem is. How can one debug this sort of thing?