Login error "You are not allowed" for everyone except Administrators

When users accounts that are not administrators (Editors, Authors, Contributors etc…) my WordPress installation now gives off the error “You are not allowed” when they try to login. I can’t remember anything that was changed except for an upgrade to 4.3. No new plugins installed.

Here’s is a screenshot https://i.imgur.com/KIyifzM.jpg

Please help