@Mark1623 We had a similar unfortunate experience just a few days before we were about to host our very first guests. We'd also taken 5 or 6 upcoming bookings at this stage.
There had been some major rainfall, and we'd been away for a few days and came home to water leaking into our Studio, floor boards, skirting boards damage etc. it was uninhabitable.
I contacted Airbnb straight away.... Explained the situation. They asked me to provide photos, the damage was obvious, and so they cancelled the reservations for me. I followed up with an apology email to all the cancelled guests. Thankfully, we weren't penalised for the cancellations. Airbnb were really understanding. As the others mentioned prior, as long as you can prove Extenuating Circumstances, you should be okay.
It took us several months to get it back to being ready to accept bookings. The hardest part was finding where the leak came from in the first place! We wanted to make certain that it wasn't going to happen to us again! I'd recommend you do the same.
Best of luck!