If it'll help at all, here's my save file. It's one hour away from the next month, so you can let the next month arrive and then check the geoscape autosave to see if the random event was generated. It's supposed to, I know I've met all its requirements; but it just won't show up, even after a couple of RNG scumming attempts. I honestly don't know what could be wrong, or if the RNG just really hates me and refuses to spawn it.