I am having the exactly the same issue. I just transferred everything from my old mac to new mac using Mac's default migration tool. Everything works just fine EXCEPT Parallels 14. I tried everything... logout from old computer, uninstall parallels from old computer completely, removing the license.xml file using terminal, etc.. etc.. nothing works. I keep getting:
This license has reached its activation limit and can no longer be used to activate new product copies.
(the old license is still working on my old mac if i try to activate it).. Currently i am using a trial license on my new computer, and hoping the find a solution... Can somebody reset my serial key so i can re-enter it on my new mac?