I've had this issue for about the past year and I haven't seen this issue fixed in any of the newer release notes, but almost every time I reboot my WHD server the license key gets zeroed out. Sometimes I can just put in my existing key from the customer portal and it reactivates, other times it won't take it and I have to open a ticket to generate a new license key.
So this happened again this morning, and even though support was quick to generate a new key it's still annoying to deal with. I'm wondering if this has been fixed in the newer version 12.4.1. I'm currently on 12.3.0. but haven't seen this issue show up in any of the newer release notes yet.