There are two reasons why this may have happened:
Your Premium membership has expired - oh no! Non-premium members can only see private and recommended sites, as well as their 10 closest pads (excluding aerodromes). If you would like to regain access to Helipaddy's full pad listings, please renew your Premium membership.
Filters have been used in the app to hide sites of different categories. To undo this, go to the map then click the filter button in the top right. Press reset and then show results to make all pads visible again.