Hi Bryant, my name is Neil, and I'm a Windows 10 user like you.
Sorry you're experiencing this keyboard issue.
The only thing that makes sense to me for what this could be is that your physical keyboard is UK layout and you have your keyboard set to US layout? A US keyboard does not have a backslash key. They normally access this by pressing the right Alt key (Alt GR) and the key with the hash symbol (#) on it.
You need to check what your keyboard layout is set to in your Windows Settings. To do this, using your keyboard, press the Windows Key + i to open Settings
Select "Time and language".
Click "Region and language".
Click the language you use.
Click Options.
Check what keyboards you have installed. I would remove any US keyboard layouts and any other keyboards you don't use.
After doing this, try your backslash key again. You may need to reboot for changes to fully take effect.
Let me know how you get on.
Kindest regards,
Neil