Having trouble with mail add on - can't configure in zoho crm

Having trouble with mail add on - can't configure in zoho crm

I have added another user license to my ZOHO CRM and purchased Mail Add on. However, I am not able to configure getting my email within CRM.

How do I send email invitation to activate? I get a message saying that "My link expired"

Alternatively, after providing all the info I get a "Read error" when I go to Personal Settings --> Email Settings --> add POP account with information