My POP access keeps being blocked (I am on a Premium account)

My POP access keeps being blocked (I am on a Premium account)

Hello,

I keep getting my POP access blocked (see attached).

The message is:  Your POP access has been blocked due to excessive usage. Use  this link  to unblock your account.

I click the link in the email which fixes the problem temporarily, but within 1 hour the problem is back!

I don't know why this keeps happening - I cannot find answer online. I am on a premium account (paying $99 per user per year).

I contacted Zoho but nobody responds. Can someone please help!