Gmail messages stopped updating!!

Gmail messages stopped updating!!

Hello,

I was able to follow all instructions regarding connecting my gmail account with Zoho through Zoho Mail Add On. My e-mail messages, slowly but surely, started updating from around 2004 on. Not sure what happened, but the updates stopped around March 2nd of 2011. I've tried everything - deleting large e-mails, re-configuring POP settings, etc. - and I can't figure out how to continue the updates and make sure all e-mails are up to date.

Can anyone help? I am going crazy here.