When I am trying to restore (moving from one server to another) our instance of Confluence I encounter a strange, not a very descriptive error:
Your session has expired. You may need to re-submit the form or reload the page
I tried two different backup files (ZIP), tried changing permissions around, etc. No idea anymore.
The new installation is a docker container (official, latest). Migrating from MySQL to PostgreSQL on the way. Besides that nothing special I would say...