Due to human (non-bot) spam the first contribution of a user has to be reviewed and activated manually, all further contributions do not require this.
As long as a user does not have at least one reviewed and activated contribution, the user is unable to edit his profile, set a avatar, title picture or a signature.
We do not support migrations for major version changes or several minor changes. The best bet you have is migrating from version to version with the original file (!). You will need to go to the backups folder in your storage folder and save the latest backup before you tried migration, then use that savegame to upgrade from your version over every next step. So if your version is 8.3, you use the 9.0 client, start the save, then the 9.1 client and start the save and so on.
It's not officially supported though, as I stated at the beginning.