Typical Windows 10 upgrade issue. I had the same thing happen, seems pretty common. I just used this:
https://www.microsoft.com/en-au/software-download/windows10 scroll to the bottom and download the media creation tool and follow the instructions there. One small difference is when it ask for your key you click "skip this step" when you login to your Microsoft account afterward it automatically activates.
This might work also and is faster:
Try this. Press Windows + X
click on "Command Prompt (admin)" and hit yes when it ask about making changes.
type in (without quotes) "sfc /scannow" and press enter and let it scan and repair.
That is assuming the menu pops up when you press win + X