I would message them on Airbnb platform/app and call/text them. I’ve only had to text two people in 1.5 years of hosting as they were not responding to my messages. I asked them to please check the Airbnb app/platform as they didn’t respond to my messages. And it also shows they did not read it but this feature could be turned off by a user too.
If you did the above and still haven’t heard back from them, I would reach out to Airbnb customer service and ask them for help to contact your guest so you can plan to meet them/greet them/orient them to the space.