I fixed it – it had to do with the database settings in PHPMyAdmin. The “siteurl” field didn’t have the WWW, the front end was being forwarded to the WWW. So when I went to “customize”, the re-direct messed up the session.
Not sure if the update this morning caused it to not actually function (it was working fine before with the inproper settings), or just a coincidence. Either way, that was the fix.
If something similar comes up in the future, that may be the reason. And you’re right, I should just disable caching when developing.
Thank you!
Nevermind I fixed it – in PHPMyAdmin in my database under wp_options I had to change the siteurl to include the WWW. The re-direct between the admin (non-www) and the actual website (re-directs to WWW) was causing the issue.
Just in-case anyone has the same issue.