Cannot open Adobe Reader DC or XI - File path not valid

I have been troubleshooting a PC owned by a family friend for the recent inability to open the Adobe Reader program; either through the .exe file, the Start Menu shortcut, or when trying to open a .pdf file. The error message comes up as something along the lines of "C:/Program Files (x86)/Adobe/Acrobat Reader/AcroRd32.exe cannot be found", and I have found a few other forum posts dating back to 2015 with this issue.

Renaming the AcroRd32.exe to anything else (i.e. AcrobatRd32.exe, reader.exe) allows the program to open and I can then open .pdf files using the programs' File>Open option. It works exactly as intended except it does not act like it should when trying to set a program to be the default viewer of .pdf files, as it will not come up in the "Open With" part of the right-click menu in Windows Explorer.

The PC is running Windows 10 Pro, 64-bit; I have run AVG on this computer and it detected a potential registry issue, so I installed CCleaner and ran its registry optimization process, which detected a number of broken registry links related to Adobe. Unfortunately none of the registry cleans fixed the issue.

I ran the AdobeLabs Reader Clean Tool over the system and restarted each time, then reinstalled first Reader DC and then Reader XI - both of them had the same issue with AcroRd.exe.

If anyone could recommend any further actions I could try, that would be much appreciated.