I have had the same problem with couple of Disc lite5.
After setting device as ap-bridge, it becomes invisible to winbox and ping.
Station side, I could connect to bridge-ap only by MAC.
AP side wise, ap-bridge was completely invisible.
Comparing setups I have found that interface list of station-bridge is fine but interface list of bridge-ap misses "bridge".
Add mannualy "bridge" and set as LAN.
After that, ap-bridge is fully available from both sides by IP or MAC.