"Incoming disabled" Operation permitted for paid user(s) only.

"Incoming disabled" Operation permitted for paid user(s) only.

I have an email address  that would not receive emails.
When I try to enable the  Incoming email, I get this error message "Operation permitted for paid user(s) only."

It seems that the account is blocked for an unknown reason.
How can I unblock the account?

Thank you for your help.
Best regards