There's usually an unspoken rule about not transferring the license within 90 days of the last transfer.
This is to prevent users from using one license shared among different devices by frequently transferring back and forth.
If you have purchase proof, you will need to contact support, see if they would be willing to manually activate for you. Explain to them why you had to change motherboard again two days after the last one. Forum users like us cannot override this.
To get help, open the "Get Help" app on your computer (just search for it in the Start menu). or go to https://support.microsoft.com/contactus, Type "Billing" and press Enter. On the next screen, click "Contact support" at the bottom of the page, then choose "Windows" > "Manage my subscription". You’ll then see the option to chat with a Microsoft support agent who has access to your account to help review the issue.