The latest Windows version is 1909, you can either do it via Windows update
or with this tool from Microsoft:
https://go.microsoft.com/fwlink/?LinkID=799445
The problem with Windows activation will not fix it.
Do you have an activation key? It's got 25 digits.
If so, we can try to activate Windows via CMD.
Or:
Activate Windows 10 by phone
Press the key combination Windows + R.
Types slui 4.
Confirms with Enter.
Selects your Country from the drop-down menu at the top
You will now see an installation ID consisting of 9 number blocks.
Calls the toll-free or chargeable telephone number displayed above.
If the computer voice prompts you to do so, enter the individual number blocks one after the other.
If the Installation ID is correct (and legal), you will receive a Confirmation ID with blocks A through H, which you should write down.
Then click on the button Enter Confirmation ID to enter it in the next window.
Then click on Activate Windows.
Here you will find the steps again:
https://www.prrcomputers.com/blog/activate-windows-10-telephone/