I recently did some configuration changes to the security of my machine, then updated Unity Hub. Much to my chagrin, it decided to explain to me that I was no longer licensed, period… no way, no how, and anything I tried to activate was invalid as well. Here’s the fix!
If you have a VPN connection, you need to copy your machine’s primary (physical) MAC address, delimit it with semicolons (XX:XX:XX:XX:XX:XX). Next, you need to start a manual activation, and open the file you saved in your favorite text editor.
Find and change it to the MAC address you saved earlier. Next, visit the manual activation page on Unity’s website (Unity - Activation), upload the file, download the new license, activate Unity Hub, and profit.
This /may/ work with other network adapters being added or removed, as well.