slmgr.vbs /ato
Option 2 – If this is your personal computer or lab
You need to change the product key to a valid retail or OEM key.
Go to Settings → System → Activation → Change product key.
Enter your genuine Windows key (for example, from the sticker or your Microsoft account purchase).
Click Activate.
If you don’t have a key, you can purchase one through the Microsoft Store from that same Activation page.
Option 3 – Convert to Retail activation via Command Prompt
If you have a retail key, you can also run:
slmgr.vbs /ipk XXXXX-XXXXX-XXXXX-XXXXX-XXXXX
slmgr.vbs /ato
0x8007007B = Windows is looking for a KMS activation server it can’t reach.