Activation key not recognised by build 1970

I think that if I had this problem, I would try the following:

Back up my VM.

Install my local Parallels version.

Without starting a VM, update to the latest released version.

Try to start the VM. If it starts, ignore tools messages, and attempt to get to the Windows control panel and use Add/Remove Programs to delete the tools installation. If that worked, I'd restart the VM, and install the tools from the menu, and that should be all I need to do.

If that didn't work, I'd get a new trial key, install the beta, use it to remove the tools (probably using a copy of my backup), then install my local version, update, start the VM and install tools.

I also think that before installing any new version, I'd uninstall the old one, and trash /library/parallels (not ~/library/parallels) just to be sure.