When you created the reaper.ini file, did you make sure you saved it as plain text (not rich text), and did you remove the .txt from within the 'get info/name & extension' panel in Finder (so Finder asks you if you want to change the extension from .txt to .ini)?
I had a similar issue earlier when I didn't take those steps. If you're using Textedit to create the .ini file, I had to go to the 'format' menu and select 'make plain text' in Mojave when saving, not sure if it's the same for Catalina...then save it, select it in Finder, hit 'command i', go to the 'name & extension' triangle, open it, uncheck 'hide extension' if it's checked, remove .txt from the file name just above that, and you should be asked if you want to change the file extension from .txt to .ini - click to change to .ini, and you should be good. Here's a Kenny video that walks you through it:
https://www.youtube.com/watch?v=PlsLEc5cvEM