Here is a fresh portable Reaper install, I added a couple of toolbars, one at the top that helps to add tracks and then a toolbar#2 with the "transport stop playback at end of loop" in it.

https://drive.google.com/file/d/1AL2BCD0nn-RwQSJv89_RhwFYGfZOQKg4/view?usp=sharing