I cannot deactivate my Trados Studio 2021 Freelance license to activate the Freelance Plus license

Last year I bought the upgrade to Freelance Plus and I have been trying to deactivate the license of Tradost Studion 2021 Freelance for quite some time now in order to activate the Freelance Plus one. I have tried different browsers, but I am still getting the same error message.

Deactivation failed. Login for this product key has been restricted. Contact the system administrator for assistance.

Even logged in as an admin to Studio does not solve the issue. Could you maybe assist as I need to start using the product? 

Thank you very much.