Hello Ethan C,
Based on what you've described, I think the key detail here is that this machine originally came as a prebuilt system with Windows already activated.
When a prebuilt PC includes Windows from the manufacturer, the license is often an OEM license tied to the original motherboard. Replacing the motherboard is generally treated as a new device for activation purposes. That would explain why activation was lost after moving from AM4 to AM5 and why the Activation Troubleshooter cannot find a matching device, even when signed into the same Microsoft account.
Error 0x803FA067 is commonly seen when Windows cannot find a valid license to activate with, but the more important question is what type of license was originally used.
Could you clarify a couple of things?
• Was Windows already installed and activated when you bought the prebuilt PC, or did you purchase a separate retail Windows license yourself?
• Was the motherboard replaced as part of a manufacturer warranty repair, or was it a personal hardware upgrade?
• In Settings > System > Activation, does it previously show "Windows is activated with a digital license linked to your Microsoft account" before the hardware change?
If the system was using the original OEM license that came with the prebuilt, and the motherboard was replaced as an upgrade rather than a warranty repair, a new Windows license may be required.
If, however, the license was a retail license or the motherboard replacement was handled as a warranty repair, there may still be activation options available.
Those details will determine the correct path forward.