@Chris14676 Airbnb has a lot of tech glitches. A couple years ago I also stopped receiving text alerts. After I reported the problem it took several weeks to start getting my alerts again.
It's always a good idea to check at least 2 methods of getting alerts, so if one fails, hopefully the other still works.
As for hosts not responding in a timely fashion, there hasn't been any system change, but it's hard to know why this would happen- it could just be the case of an unresponsive host (and some cultures are more "mañana" oriented), but it could also be quite innocent- the internet could be down where they live, they might be somewhere out of range, the host might be ill.
I've had guests not answer messages and thought they were just ignoring me, but that turned out not to be the case.
One thing I can tell you is that Whatsapp is heavily used in Mexico and Latin America and is the preferred method of communication. Because it's free as long as you have a cell signal, whereas internet may be expensive.
So you might try using Whatsapp text or phone call to simply ask the host to look at and respond to your Airbnb message on platform.