I have been playing my same vault on Fallout Shelter for a while now. I have 40 dwellers. I haven't had one attack yet. No mole rats, raiders or death claws. My first vault I had an attack at least every other time I played the game. It's getting kind of boring.... most issues I have is fire/radroaches when I fail at rushing a room. I send people out on explorations often. I have an upgraded radio room with 3 people working in it. Help? I want some attacks :-)
There's really only two options:
- You are experiencing a bug as others have commented, you can contact support to report it, or start a new game (ugh, I wouldn't)
- You are just ridiculously blessed by the RNG gods and sooner or later you'll get your first attack. Those are RNG based events, but I thought that over time the chances of getting one increases to the point where it's inevitable, but I could be wrong.
Personally I'd be happy with no mole rat attacks, I hate having to station people all over and not working in generation rooms or skill rooms.