As a freelance translator, I am currently working with a Trados Studio 2021 Freelance Plus license (which is actually an upgrade from Trados Studio 2017 freelance plus to Trados Studio 2021 Freelance Plus). As I have received a RWS mail telling that the 2021 version will no longer be supported at the end of the year, I decided to order an upgrade from SDL Trados Studio 2021 Freelance plus to SDL Trados Studio 2024 Freelance plus for € 447 (instead of € 745) before September, 30th (Trados 40th birthday offer).
I selected :Upgrade from Trados Studio 2021 Freelance Plus to Trados Studio 2024 Freelance Plus", then I clicked on "Proceed to checkout". I surprisingly received this error message :

Can you please tell me what the problem is due to ?
Is it because it is impossible to upgrade an already upgraded version of Trados ?
Or is it because my both licenses are activated ?

Many thanks in advance.