How to solve : You do not have sufficient permissions to access this page
If you upgrade WordPress and get:
WordPress Error: You do not have sufficient permissions to access this page
you might have had a problem whereby WordPress thinks you’ve completed the upgrade but in fact some things have been left unfinished.
If this is the case, you can find a fix here. You’ll need to download a fix and run it on your server but I’ve had great success with it fixing this problem.