The error occurs if the property type on Airbnb is set to 'House'.
On this page, you will find more information about the most common causes and most relevant solutions for the AirBnb error 'Failed: Myallocator request sent to AirBnb via API hasn't passed validation process. Details: [Invalid value: available_count. This listing's property type does not support multiple inventories]'. Do you need help straight away? Visit our support page.
Change the property type to any other type.