Upgrade error "You do not have sufficient permissions to access"

This isn’t a question. This is help to fellow confused wp’ers.

Symptoms: Whenever I tried upgrading All-in-One Event Calendar, I’d always get a “You do not have sufficient permissions to access this page.” after the theme installation, when the page would try to redirect to calendar settings. I spent a day looking and found LOTS of people with same problem with little help.

Problem: After two hours I found a tiny post on a random page that states the solution has nothing to do with permissions- it has to do with the /wp-content/themes-ai1ec/ folder. That folder is likely empty and needs the 4-sub folders from /wp-content/plugins/all-in-one-event-calendar/themes-ai1ec/

Solution: copy the four sub folders from /wp-content/plugins/all-in-one-event-calendar/themes-ai1ec/ to /wp-content/themes-ai1ec/

IMO I think this only effects people who’s servers PHP settings are set to not allow php (WordPress) to modify/move most files (i.e.: you have to enter ftp credentials when updating your wordpress blog, and/or wordpress 3.8 new auto-update doesn’t work on your installation). I think this was a slight oversight by the author as the majority of wordpress users don’t have such strong php settings.

https://www.ads-software.com/plugins/all-in-one-event-calendar/