Thanks! The minimum viable build size is closer to 50mb with optimizations. In this game jam the target was <100mb so this game has a lot of the riff-raff removed to account for that. This shouldn't cause issues but it's one that could produce a fatal start error like that. Other causes could be a lack of supported GPU/hardware or a bad download.
Anyway, i've updated the current build to UE 4.22 and also removed some of those optimizations just in case. Confusingly the file size is now even lower, but hey!
If you get an opportunity to try it again, i'd very much appreciate it!