Unable to activate license: This license key is associated with another Parallels account.

Hello,
I'm experiencing the same issue when trying to transfer my valid Parallels Desktop license to a new Mac.
I have a legitimate license key for Parallels Desktop (version 18), which I purchased and activated on my previous Mac under my own Parallels account.
Now I'm trying to activate the same license on a new Mac. When I attempt this, I receive the following messages:

"This license is already used to activate Parallels Desktop on another Mac..." - I understand and agree that activation on the new Mac will deactivate the old one.

However, after clicking "Activate on This Mac", I receive the error:
"This license key is associated with another Parallels account. Please sign in using this account and try again."

Can anyone help me?