Fix Windows 10 /2019 activation error 0x087E10BC6
  1. Click Start and type CMD in the Start Search menu
  2. Right Click and choose Run as administrator
  3. To remove any existing product key (in case you used a trial key), enter and run the command slmgr.vbs /upk .
  4. Clear the product key from registry by running slmgr.vbs /cpky
  5. To enter your new product key, use the command: slmgr.vbs /ipk xxxxx-xxxxx-xxxxx-xxxxx where the x’s are your actual product key.
  6. Lastly, activate Windows by entering the command slmgr.vbs /ato
  7. Windows is now activated.

to check windows activation status type:

slmgr /xpr and hit enter