I installed version 17, and when I upgraded 18 and was ready to activate, I was prompted to enter the upgrade key and asked to enter the key of the previous version. I entered the version 17 key indicating that my old activation key had not been accepted by the license server
Hello, Thank you for your feedback We have verified the 2 keys. You should now be able to activate your Parallels Desktop 18 with the Parallels Desktop 17 license key. Let us know if it resolves the issue. Thanks