AFAIK the mode “ap-bridge” has been renamed to simply “ap”, see:
http://forum.mikrotik.com/t/ap-bridge-missing-on-cp-ax-capgi-5haxd2haxd/173140/9
The other side should be set in station-bridge mode, as both devices are Mikrotik:
https://help.mikrotik.com/docs/spaces/ROS/pages/122388518/Wireless+Station+Modes