@Ona7 This happened to me about a year and a half ago. You don't say when they were supposed to check in, or how long they were supposed to stay, but here's what I did, and it worked out for me.
Message the guest on Airbnb messenger, if you haven't already. You can also try calling them, but make sure that there is a record of you contacing them through the messenger app specifically, so Airbnb has a record of it if the guest requests a refund. If it's been more than a day since they were supposed to check in, I would message Airbnb and let them know that you guest was a no-show. Explain that you haven't been able to contact them, and express concern for the wellbeing of your guest. They will likely try and contact the guest to find out what's happening. Maybe the guest will respond, or maybe they won't, but at least you've shown that you're taking action to try and assist them.
If the guest does respond, I personally wouldn't offer them a refund, as they have blocked your calendar and they should have cancelled if they're not coming. However, as you're a new host and the guest will still be able to review you, I would consider giving them one if they ask for it: reviews are critical when you're new. This is assuming that the stay was short and they weren't holding your calendar hostage for multiple nights.
In my case, the guest never turned up or cancelled and never asked for refund. I kept the money. They also never reviewed me. Fingers crossed that your experience will be the same.
