Hi @suzed4, welcome to the forum
Which ArduSub version are you using? There was an issue with ArduSub 4.1.1-beta2 that prevented the relay functionality from working properly. 4.1.1-beta3 has since been released, so it may help to try installing the latest beta.
There is no parameter with that name. Presumably you mean RELAY_PIN
?
Have you got a lights or camera mount output assigned to channel 14?
SERVO14_FUNCTION
should be Disabled (0)
, and servo14_raw
in the SERVO_OUTPUT_RAW
message (in the MAVLink inspector) should toggle between 0 and 1 when you press your relay toggle button.