Clarification. I realized that when I go to the map, the terrain map does not load at all, only regular map and satellite map load. I initially thought the terrain map did load before I downloaded the offline maps to my phone, but after giving it some more thought, I believe the terrain map only loaded when I was using the free version of this app, right before I purchased Pro. Perhaps this is the problem, not necessarily that Terrain maps are not downloading properly in offline maps/guides, but terrain maps are not loading at all in Pro; when I downloaded the offline maps, the only map type option I had was the Terrain map.
Thanks for your help Chris!