Update: I just performed a clean install, as follows:
1. I activated and logged into the Administrator account on my PC.
2. I uninstalled the program.
3. I deleted the related files/folders under ProgramData and Program Files.
4. I rebooted my PC and logged back into the Administrator account.
5. I reinstalled the program.
6. I ran the program for the first time as an Administrator.
7. I entered my registration name and key, as provided via email.
8. The program successfully shows as being a "Registered Copy" when run under any/all Windows User Account on my PC.
However, the problem persists. When I select and right click on a group of files in file explorer and select "Rename with MFR7" from the context menu I get the following error message:
"You must run the program for the first time with administrator privileges."
Windows 10 64-bit version 1709 (Fall Creators Edition)