Can't reset customer's access to the support portal

Can't reset customer's access to the support portal

I have a customer that can no longer get into the Support Portal. gfdc2@fremontne.org had access but no longer does. When I try to re-invite, I get a warning "This contact email already exists." I have tried deleting the contact and reloading but this doesn't work either. Please advise.
Thank you!
Heidi