OK. Two questions.
1. Look in the gs_AppSettings table and tell me the value you see for the record where SettingName='DataSchemaVersion'.
2. Can you send me your web.config file? Mask any SQL passwords in there for your protection. I want to make sure it is pointing to your SQL Server providers.
One note: You should not have received the message "Not needed: Version 2.4 and higher does not use galleryserverpro.config" the first time you ran the upgrade, since at that moment the database should have still been at the 2.3 schema (when the schema is 2.4.*, that message is shown). However, you may receive that message if you try to run the upgrade wizard a second time after a failed first attempt.
Roger Martin
Creator and Lead Developer of Gallery Server Pro