pbdrmmr said:
It should work if you paste the whole line into the File Explorer address line (assuming that your settings show that).

On my machine the whole line resolves to
This PC>HP(C: >Users>[MyName]>AppData>Local>Microsoft>Windows>Themes

The directory AppData is a hidden directory. To see it, at the top of File Explorer, click on View. On the far right, click Options>View and choose Show hidden files, folders, and drives.

Hope this helps.
Hi,

I have just had the same issue after uninstalling a theme that I installed recently. Try going to %windir%/Resources/Themes
or %USERPROFILE%\AppData\Local\Microsoft\Windows\Themes and see if you have any more theme files. Delete all of those and restart your computer, it should be working fine now :)

Source.