Curiosity got the best of me so I downloaded and checked the lot out myself. The routing problem is on the pathway area right before the stairs into the house proper. To make it functional, just go into build mode and use the terrain tools to smooth that section of pathway a bit more for the 10-15' right before the stairs. Basically from the bottom of the stairs to the 2nd building down. Took about 3 seconds to fix it.
Only problem then is, once it is fixed, I couldn't get enough flat terrain for the Humidor shed that is beside that building right by the house to remain. I didn't try very hard though.
Edit to add: Just a suggestion, but if you want to try to preserve that shed, maybe put a wall around it so it is considered part of the little building itself...then smooth the terrain. That might preserve the terrain under the shed so that it can stay there. I already exited the game when I thought of that, but figured I'd share the idea if you want to try it @CaioSantos.