hi jacob i am facing the same issue i am using pixhawk 2.4.8 and i am using mission planner 1.3.72 what should i do
@zukhraf Its sounds like a hardware issue with the Pixhawk 2.4.8. We don’t sell that version version, because there’s a lot of documented hardware issues: Search results for '2.4.8' - ArduPilot Discourse
ArduSub is only supported with QGroundControl. Why are you trying to use Mission Planner?
I had the same problem and it solved with this steps. thank you