I have a licence for 2021 & 2022 but can't activate 2021

On a new PC I have just installed Studio 2022 and activated it. But I wonder why I can't activate the 2021 version. 

I have Studio plus licence and with the optional parallel activation of 2021. 

Any ideas?

PS

When I see "A well formulated question triggers better responses!" all the alarm bells ring. It makes it sound as if Trados Support doesn't even know its own products.

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