@Amy2697 this must be so frustrating!
This is a host community so none of us can help you. Perhaps try to reach out to them through social media or open a chat. I have never heard of them not responding for so many months.
On a personal note, I use a device called party squasher so in a situation like this two things would have happened
1. I would have known in real time they brought so many extra people and could ask them to leave immediately. You could have called Airbnb party line and they would have assisted. At a minimum, this would have been documented and made your support case easier plus the guest could not have left the review
2. If you did not catch it in the moment or could not deal with it, you would have had the party squasher record to collect from the guest