Problem with accessing CRM

I have received the invitation to join CRM from my company admin but get an 'account disabled' message when I put in my email and password. We have tried deleting my account then setting it up again, lots of repeat invitations, change of password, several different laptops, ipad app, going out and using someone else's broadband connection, with no joy.
I can access my zoho email but seem destined never to use the CRM - Any advice welcome.