If you try and activate a WIndows 2019 server using a (valid) MAK key, it fails. it’s a known bug and folks have been very vocal on a lot of communities.
At this stage, I’m also aware only of the command prompt workaround (cscript c:\windows\system32\slmgr.vbs /ipk <product_key>).
Its not the issue of the key itself but in the design from what I understand. So, I don’t believe you’d require a new set of keys as the old ones do work. Just slmgr command line is the way to go