That is why its ROM and not CAP.
CAP mod will fail security and you have no USB BFB feature on that motherboard model, read the linked guide.
EDIT: Did you perform a safe keep backup of the bios, before any flash mod? You should as it contains motherboard/system own data.
Did you performed the mod from another user file or used another user file?
Retail/End user motherboards do not contain embedded MS KEY/Activation unless from specific OEM/Assembled systems. On old bios backup if exist such data, its there and if the mod was done from the backup file it should be there also.
No backups we cant do nothing…and theres plenty of ways of a working OS loses his activation on several user actions and hardware changes, you may think that you has a mb with PK and its just an hardware change…presuming only from my point of view.
Still besides MS PK theres a manual way to add SN and MAC to it.