I discovered this thread because text alert sounds were not working on my iphone 4 (yes in 2016). I didn't even know whether the call alert ringer was working because people don't call me very much, they text me and those sounds text weren't coming in. Anyways, took my phone out of the otter box for once and got curious about the little switch on the left side. Switched it from down to up (no orange showing). Text alerts now work. I guess it's the silence button. Didn't know that until now. I've had the phone in use almost 6 months now, but never looked into the little switch until today. This might solve the issue for a few of the more antiquated and dense people like me who use 5 to 10 year old computing products and don't pay attention to any of the features or apps.