Well, I can't tell without debugging unfortunately. It can be anything.
In case you had an older version installed, you should try to go through the secure update steps, it usually helps: https://wp-dreams.com/knowledge-base/updating-from-older-versions/
Don't forget to open up each settings page and save them again. It might be just an inconsistency with the options database.
If you like my products, don't forget to rate them on codecanyon :)