Office 365 Unable to access due to my email address

I upgraded to Sage 50 Accounting with Office 365.  I am unable to access the Office 365 due to my email address.  I spoke with the helpdesk and they said my ISP is blocking them.  They want me to open a gmail account.  Is anyone else having this problem?  I am using a webmail account.  The same one I have used for my business for 20+ years.