The USB Flash Creator stops with an error if it is run under an account name that has some kind of special characters in it.
In the example in the picture, it is the character "å" in the username Håkan that causes the error.
Using an alternative account with the username Hakan instead, the USB Flash Creator works just fine.
Discussed since 2018:
https://forums.unraid.net/topic/76084-usb-flash-creator-on-windows-10-error
Do you have some special character in your account name?
In my normal "Håkan" account, I just got this error, so I had to switch to my "Hakan" account.
Then the USB could be created just fine.