Adding a guest not working?

[Wendy12]

I am trying to add an extra guest to a booking for the customer, usually I can just add the extra person and it automatically updates the cost to an extra $10 a night. But now it says our property can't have more than 4 guests so I can't do it...yet I looked again to ensure the extra guests thing was still on and it is. What can I do now? I tried to update the price as well and that doesn't seem to have worked either. The guest is waiting for me to send it and here I am mucking about!

I would appreciate some advice on how to contact Airbnb or get the options to work. thanks!