Resetting your application data is the "quick fix" for anything that may go awry with Shift.
To do this you will need to do the following:
1. Go into Settings (the wrench icon located in the bottom lefthand corner of Shift)
2. Go to the General tab (second from left)
3. Scroll to the bottom and select 'Reset Application Data'
5. You will be presented with an alert describing what is about to occur
6. Click 'Proceed'
7. Shift will shut down and then restart immediately on its own
8. You will be presented with a screen to add accounts
9. At the bottom, you will see a link to log into your Primary Shift account -
click on that link and log in.
10. All other email addresses adding to Shift will automatically populate
10. Re-authenticate your accounts by entering your password and logging in
Note: You will not need to re-add any of your other email addresses, simply login using your password and away you go!