Ok, let me know if this works for you. I pin various email accounts to my start screen, well one of the updates the live tile correctly and the other doesn't. So I began trying to find the differences (gmail versus yahoo...). I think the issue is a common developer bug where they don't handle lists correctly. Yahoo was my first listed email in Manage Accounts...and it DID NOT WORK. I deleted it and added it back in to where it is at the bottom and my Windows Hotmail account (which I don't use for email) is at the top of the list.
Now both my gmail and yahoo live tiles appear to work.
See if it works for you.
Now both my gmail and yahoo live tiles appear to work.
See if it works for you.