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 <Binding Key="5" Value="XX:XX:XX:XX:XX:XX" /> and change it to the MAC address you saved earlier. Next, visit the manual activation page on Unity's website (https://license.unity3d.com/manual), 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.