Hello,
For me it was the following: I frequently use a bluetooth headset and/or headphones for calls and music and I also have bluetooth speakers.
Go to the settings for the text message tones. I assume that when you change the tone, you get vibration feedback, but not the alert/ringtone, when you change.
Now swipe up the "quick menu" from the bottom of the screen (i.e. where you can switch on flashlight, wlan, bluetooth etc.).
There click on the little presentation-like icon (Airplay) and check if it is set to iphone or bluetooth. For me it was set to Bluetooth.
And yes, you can have it set to Bluetooth, even when you have Bluetooth radio disabled. That is the problem.
When it is set to that, texts, calenders etc. sounds won't be playing. So switch the AirPlay to iPhone.
Hope this solves it for somebody.
phph