CANT REACTIVATE MY WINDOWS 10 DIGITAL LICENSE AFTER HARDWARE CHANGE

Since you have changed your motherboard, this is a hardware change.

1. If Windows was preinstalled i..e OEM version, then you can not use the license on another hardware. OEM license is tied to motherboard and if motherboard is changed, you can not reuse the same license on new motherboard.

In this case, you need to buy a new license.

2. But if it was Retail license, then you can follow the below process

To Reactivate Windows 10 after a hardware change, refer to following Microsoft Help -
https://support.microsoft.com/en-us/help/20530/...

For problems in activation, you can also reach out to Microsoft Support for activation help. They can work with you on this to resolve activation issues.

By Live Agent Chat - https://partner.support.services.microsoft.com/...

By Phone - You can talk to support by picking up appropriate country
https://support.microsoft.com/en-us/help/13948/...

3. If above doesn't work, To analyze the cause, I need to verify whether it is OEM or Retail or Volume and other details, I need the screenshot of following output
Windows Key+X > Click on either Powershell (Admin) or Command Prompt (Admin)
Copy below and paste into Powershell / Cmd windows and Enter
slmgr.vbs /dlv

It depends on how Windows 10 was originally configured on your computer.

If its a full retail store bought license online or offline, it is transferable to a new computer or motherboard.

If its the free upgrade from a retail store bought Windows 7 or Windows 8 license, it is transferable to a new computer or motherboard.

If its the free upgrade from a OEM preinstalled Windows 7 or Windows 8 license, it is NOT transferable to a new computer or motherboard.

Learn more about transferring your license:
http://www.groovypost.com/howto/transfer-window...

If its a retail license, learn how to reactivate:
http://www.groovypost.com/howto/activate-window...

You could try chatting with support agent and explain the situation in detail and they might be able to activate it. We were able to confirm with Microsoft under some circumstances, OEM licenses can be reactivated even under the free upgrade offer. Its not guaranteed every support agent will do it though, but you can try your luck.

Microsoft's view is, as long as you are not abusing the license, you should get a pass.

Activate Your Windows 10 License via Microsoft Chat Support
Use the following link to directly reach a live agent who can assist you:

https://partner.support.services.microsoft.com/...

You have a retail license, so all you need to do is contact chat support and explain the issue and they will reactivate it for you:

https://partner.support.services.microsoft.com/...

You can also call support:
https://support.microsoft.com/en-us/help/13948/...

Information in the above link is sourced from a trusted Microsoft MVP Blog.