Huh, I wasn’t aware there was a direct Ping Sonar rangefinder option in ArduPilot. It’s seemingly from before I started at Blue Robotics, and doesn’t seem to be mentioned in our documentation (which is a situation we should improve/fix).
Ok, good that you seem to have found a workaround for your issue at least 
I’m not sure - do you have access to a multimeter? You could potentially probe the port without the sonar connected to see if it’s providing an output at all or if the power pin is fried/damaged.
I’d recommend you contact support@bluerobotics.com for this - I’m not sure what we normally suggest when the epoxy on a potted penetrator has failed. If the device is still working then you may be able to clean off the electronics with some isopropyl alcohol and replace the penetrator (and possibly replace the cable too, if it’s starting to corrode), but if the PCB or the components on it are corroding then depending on the damage you may need to replace the PCB or the entire device.