Did what it says on the tin. Not giving five stars because the code was initially rejected, but a phone call to microsoft tech support fixed that issue very quickly, with no further complications.

long story short, I was trying to upgrade my brand-new ASUS ROG Zephyrus 16 that comes with Win11 Home, to Win11 Pro, but the normal activation method did fail, Microsoft was not recognizing the license as new (error code 0xC004C008). after contact SC Support they send me the instructions to activate the license by calling Microsoft, well believe or not that worked, the process is fully automated, just go to System> Activation> click on Activate by phone, follow the prompts (Microsoft will send you a link) you will need your Installation ID. You will see it after you click activate by phone.