@Erik1434 Good advice from @Lawrene0.
I always caution hosts to keep communication in the AirBnB messaging system whenever possible. That way there's a record of everything that's been said and done. Once you text a guest, it opens the door to outside communication, and if you ever run in to problems, that can be a complicating factor.
When I have upcoming reservations, and the communication has been erratic- like it seems that they are waiting to respond until they get to a computer- sometimes I include a gentle prompt in my messaging to try to get them to use the app. Something like, "I keep all communication on the AirBnB platform, so if we need to communicate during your stay, please make sure you have notifications activated so you'll be able to receive messages." You can generally tell my their communication patterns if they do or don't.
I've had some older guests who struggled with the app, and it did cause problems with messages.
Good luck with your hosting! Kia