This isn’t the first time we have seen something like that
Generally the first thing that is looked into when a route can’t be found is to check the coordinate order (often latitude longitude is given rather than the correct longitude latitude). If that is all fine then 9 times out of 10 it is something to do with the OSM data , so then it is just a case of moving the start and end points until a route is found and then from that looking back at what would cause the route to not be possible. Normally it is a case of a gate, very new OSM data that isn’t in our routing graphs yet, or that a road or path is tagged in a way that it wouldn’t be suitable for the particular mode of travel.
So nothing too magical lol
I would definitely recommend looking into how to edit OSM as it is a really great resource, not just for routing but for many other projects as well, and what people contribute can make a huge difference on people’s lives (a lot of humanitarian organisations use OSM for disaster relief, for example)