Hi @VioletCheese,
- Which ArduSub version did you base your custom firmware off?
- Which QGroundControl version are you using, and on which operating system?
- Are you able to try our latest recommended version(s)?
Your issue sounds similar to (but potentially more severe than) this one, where QGC doesn’t fully register the vehicle as Sub.
- Do the workarounds in the Detailed Description section of that issue work for you?
- Does it help to use BlueOS instead of the Companion Software?