So I recently figured out a problem that I had to deal with for 2 days.
I've been getting the same error for 2 sites that I am developing. (see attached image)
Long story short, the fix is to set the permissions of the `/assets`, `components`, and extra's folder to 755.
Don't just set the connector.php's permission to 755, set the folders' above it as well.
Don't just go looking for the 644s, check out the 775s too.
I hope this lessens your headaches.