Airbnb promotes the self check-in, along with other options, as opportunities for VRM to stay competitive in the market.
Given that Hostfully PMP is the source of truth after your sync via API to Airbnb, below is the instruction on how you can activate it from Hostfully PMP.
The setup is under Property's Main Settings. You can get there under your Hostfully PMP Agency Dropdown > Properties > Choose the property.
There are 3 requirements to activate self check-in amenity on Airbnb
1. Choose relevant check-in options (left bottom of the Main Settings tab)
2. Make sure you Set instructions for above Check-in Option
3. Make sure you have Access details (Description tab)
On next sync (either routinely or manual), your property on Airbnb should have the Self Check-In amenity.
Reference from Airbnb help article, with below excerpt:
Hope it helps, and please let us know via popup chat or email to firstname.lastname@example.org if you have any questions.