Here is the timeline: 1. In about 2016 I upgraded to Mac OS X Mavericks, from Snow Leopard. Almost immediately I activated Parallels 10 (a download activated according to instructions in an empty box) and created a VM for Snow Leopard Server, to run older software. 2. 2 years ago I upgraded from an iMac i5 to an iMac i7, but didn't change OS (still 10.9.5, as now). 3. In 2018 I changed my email address as the ISP ended their email service. Through all of this I continued to use Parallels 10, and was running 3 VMs (10.6.8, Sierra, and recently I set up a Mavericks VM "to see if I could"). 4. Last week, the i7 hard drive failed so I went back to the i5, cloning the i7 to it. (Same OS and software, no changes). Today I tried to launch one of the VMs and got this error: However, this makes no sense as I activated Parallels years ago, and have never been asked to do so since. Theory: Parallels has detected a change of machine and requires reactivating. When my i7 comes back from repair, the problem will disappear and things will run smoothly like before. Is this a good theory? If not, what should I do?