pop mail

I have an email account on one of my domains set up to be brought in by Zoho Mail. I also have Gmail set up to bring in mail from that account. Gmail has been instructed to leave the emails in that account on the domain's server. When I send a test email to my domain's account, Gmail pulls it in just fine. Zoho Mail is still waiting - after nearly a half-hour. I have Zoho Mail's settings set to check the account ever 3 minutes.

Do I have to stop using Gmail for that account before Zoho Mail will bring it in or might something else be going on?

Thanks,
- Bal