Cannot sign into Apple Mac AppStore After entering my password to update apps on the MacAppStore, I get the spinning cog and have to Force-quit the AppStore app. This also happens with Xcode.

I've tried logging into a new user account, but that also will not let me log in.

I'm able to log into all accounts on another computer. 

I'm on OSX 10.11.x

Has anyone else seen this? I could not find relevant questions.

Thanks
It seems that you may need to reconfigure your computer's iCloud. You can achieve this by reinstalling OS X. Then it would allow you to set up your iCloud account from start out. Before beginning, I strongly recommend you backup your computer just in case something goes wrong


Restart your Mac
When you hear the start up chime, hold Command ⌘+R
Click "Reinstall OS X"
Follow the instructions listed


If that doesn't work, you may need to fully erase and restore from backup.