Free upgrade to Windows 10 Pro 2019

Instructions:

Activate Windows 10 Professional without a product key:

Step 1: Run Command Prompt as administrator.

Step 2: Execute the following 3 commands separately and press enter at the end of each line.

slmgr /ipk VK7JG-NPHTM-C97JM-9MPGT-3V66T

slmgr /skms kms.xspace.in

slmgr /ato

Step 3: Press Windows + R key to bring up the Run dialog box and type "slmgr.vbs -xpr" to confirm whether your Windows 10 is activated or not.

Then reboot.

Link: https://answers.microsoft.com/en-us/windows/forum/windows_10-win_upgrade/free-upgrade-to-windows-10/a1906d5c-2183-4064-af8e-e6650c15d96d

Otherwise:

slmgr -rearm

Will give a bit more time...

slmgr /dlv

Will show some info....