Free shuttle bus to Hong Kong Airport Express Station

Generally speaking, you need to show proof of eligibility including AE train tickets (Single Journey, Same Day Return, Round Trip, Airport Express Travel Pass), Airline ticket / boarding pass, Airport Staff Octopus Card, AsiaWorld-Expo entry pass or event ticket. However, when you arrive at the free shuttle bus stop, you can explain your situation to the staff. And in most cases, they will allow you to take the free shuttle bus to the AE Station.
Good luck!