@Dean-and-Kathy0
you don't have to do anything. If your guest doesn't cancel you will be paid
however
it would be wise to send your guest a message through the Airbnb messages and ask him when he intends to arrive today as your check-in time is between xx and xx hours and you are waiting and would like to plan your day.
If he answers then you have a proof he didn't show when he was supposed to.
You can also contact Airbnb and inform them you have a no show guest, just in case your guest come up with some crazy story (like he arrived and couldn't enter the property for example) and asks for a refund.
I had a no show guest a few days ago, they booked 2 nights on May instead of June and didn't realize the mistake until I messaged them. It happens.