Try setting CAM_TRIGG_DIST to 1 and then put your hand over the GPS to reduce the accuracy. The plane’s position will start to move around the map and every time it moves more than 1m the camera will trigger. If not, this is a problem with your chosen parameters or camera or cable, not mission planner.
Are your triggers PWM based or relay? Relay should be no problem, if its PWM based it may require the aircraft to be armed.
You can trigger taking photos from MP by right clicking the map on the flight data screen and selecting the “Trigger Camera NOW” option (this is more reliable then the 1m trick).
I haven’t flashed 3.6 yet but master from 2 days before 3.6 went out didn’t have any problems triggering cameras. (I use relay setups primarily)
Yeah I was referring to CAM_TRIGG_TYPE 1 (and then you would need to configure the CAM_RELAY_ON and RELAY_* parameters appropriately) this isn’t a drop in for PWM in general it depends on your camera or IR board which is the correct type.