It seems that Windows changes the computer ID with some updates (?), which affects anything that depends on the computer ID for identification. With XLN I agree it's a hassle, but at least they make it pretty simple. You run the online installer, de-authorize your computer ID, then authorize the new one.
 
FWIW with software that allows to key to a hard drive/computer or iLok, these days I'm choosing iLok for this kind of reason.

As far as I remember the computer ID is created from the disc id where the O/S boot system resides on (usually the C: drive) and the version of Windows. Unfortunately with Windows 10 every new build (typically every 6 months) will change the key hence the issue whereas before it only changed when you went from windows 7 to windows 8 for example. It also used to use the MAC address of the network card but I think that is no longer used.
It was basically set-up to enable Microsoft to track whether a PC had a valid license for windows or not and is somewhat redundant as all future windows builds are effectively free.

werewindle
As far as I remember the computer ID is created from the disc id where the O/S boot system resides on (usually the C: drive) and the version of Windows. Unfortunately with Windows 10 every new build (typically every 6 months) will change the key hence the issue whereas before it only changed when you went from windows 7 to windows 8 for example. It also used to use the MAC address of the network card but I think that is no longer used.
It was basically set-up to enable Microsoft to track whether a PC had a valid license for windows or not and is somewhat redundant as all future windows builds are effectively free.

The things I learn from this forum...