I have this same issue. Tried with Fences 2 and 3. Both do the same.
I've tried the steps outlined above and same issue still exists.
I just had my PC reinstalled and it is running Windows 10 Pro Build 10.0.18363. Before the re-install, Fences was working fine. Since all the same software installed previously is installed again, the only difference is the Windows 10 version running now is newer.
Error I'm getting is "Fences has detected that Explorer was not closed properly. As a precaution, Fences has been temporarily disabled. To re-enable Fences, right click your desktop and choose "Enable Fences"."
If I choose to Enable Fences, same thing happens and same error pops up.