Hello @Bikerharry,
I hope you are doing well, and thanks for reaching out. We're sorry for the trouble you had.
Please note that Acrobat 2020 is now an end-of-support product. To learn more, check this article: https://adobe.ly/4557xVi
So, suggestions may or may not work.
Start Acrobat as an administrator. Right-click the Acrobat icon > "Run as administrator," then sign in and let it activate. If that stops the loop, the cause is a permissions problem, so continue with step 2.
Check this article to resolve any folder permission issues: https://adobe.ly/4xhkdV5
If the old PC is still activated, the new one may not be able to activate. Open Acrobat on the OLD PC and choose Help > Sign Out or Deactivate. Check this article for more information: https://adobe.ly/3RteIn9
If the issue still continues, please connect with the technical support team via chat, so that they can assist you further.
Please let us know how it goes, and reach out if you need any assistance.
Regards,
Anand Sri.