Why is my purchased windows 10 pro license not working?

[DempseyTorhan]

I have recently purchased a Windows 10 Pro license, intending to upgrade my computer from Windows 10 Home Single License to Windows 10 Pro using this key. However, I am encountering an error message when attempting to enter the key. I'm puzzled as to why this is happening. Are you able to provide any insights into the possible causes of this issue? Additionally, I have also tried removing the existing license and adding the new license, but it is not being accepted. I want to emphasize that my license is entirely legal and was purchased from a trusted partner vendor. Could you please suggest any potential solutions to help resolve this problem?

[DempseyTorhan]

There are a few possible reasons why this might be happening:

The product key may be invalid or expired.
The product key may be for a different version of Windows than the one you are trying to install.
The product key may have already been used on another device.
There may be a problem with your internet connection.
There may be a problem with your Windows installation.
To try to resolve this issue, you can try the following:

Make sure that you are entering the product key correctly. Product keys are 25 characters long and are made up of groups of 5 characters, separated by hyphens.
Check to make sure that you are trying to install the correct version of Windows. The product key you have will only work for a specific version of Windows, such as Windows 10 Home, Windows 10 Pro, or Windows 10 Enterprise.
If you are sure that the product key is valid and for the correct version of Windows, try activating Windows over the phone. To do this, press Windows + R to open the Run dialog box, type slui 4, and press Enter. Follow the on-screen instructions to activate Windows koows echat over developerbook the phone.
If you are still having problems, try running the Windows Activation Troubleshooter. To do this, go to Settings > Update & Security > Activation and click Troubleshoot.
If you have tried all of the above and are still having problems, you may need to contact Microsoft Support for further assistance.

Additional tips:

Make sure that you are running the latest version of Windows.
Disconnect from the internet and try activating Windows again.
Try activating Windows in Safe Mode.
Try activating Windows using a different user account.
I hope this helps!