Fortinet/FortiCloud user is disabled

Hi,

A customer of mine previously had a Fortigate device, for which the subscription expired in 2023. At the time, he had created a Fortinet/FortiCloud account for it. Now, he has purchased another Fortigate with subscription and would like to assign it to the same Fortinet account again. He still has the login credentials. However, when he tries to log in, he receives the following message: "This user is disabled."
How can the account be re-enabled?

Best regards,
Karsten