When looking at the docs for gimbal install it says to “make sure that ch7 is above 1800” Mine is 1550 and nowhere does it say what to do. Is this a tx programming issue or something in Mission planner?
You most likely need to increase the pwm value (percentage) of Ch7 on your transmitter.
Increasing the Ch7 percentage to 100% should get you close to 1800us. I believe that you can go to 125%.