I'm experiencing the same problem: Workflows appear as upgradeable, but after updating via the "Workflow Gallery" nothing changes. The update symbol remains in place, but the workflow shows no content when clicked on in the list view. After closing the preferences window, it is as before (listed as upgradeable).
I'm using Alfred 5.5 on two MacBooks. The file "Alfred.alfredpreferences" lies on my iCloud-drive and is used by Alfred on both MacBooks. The path in the preferences window is set correctly. I do not use a VPN.
Is there any solution for this issue?