Hello
A digital license doesn't mean it is transferrable. OEM and retail licenses can be both digital these days, but OEM is not transferable, while retail is.
You mentioned a pre-installed Home version. Did the device originally come with Home preinstalled, and did you later purchase a Pro license to upgrade it? Or did the new motherboard come with the pre-installed Home edition? I am sorry, but that part is quite unclear.
If you purchased your Pro license, did you purchase it from Microsoft directly or from a third party?
Did you purchase it as a full copy or an upgrade license?
Windows licenses have a lot of nuances. I would like to get all these answered first if you don't mind, as troubleshooting can take different directions.