Hi Cameron,
Not sure where you got that link but it seems to have an extra slash (before the hash #). It should be like this instead 
I searched the forum for the incorrect link and found a couple of examples of it, which I’ve now corrected in those posts. Let me know if you got it from somewhere else.
Out of interest, does the Ping1D get detected by the companion computer? You should have something like FT231X_USB_UART in the “Detected Devices”, and pingproxy and pingmav should be present in your “Active Services” on the System page of the companion web interface (http://192.168.2.2:2770/system). Note that pingproxy and pingmav only start if the ping is detected on startup, so you’ll need to plug it in before turning on the ROV (or reboot the RPi via the companion interface if it was already powered on).
Tangentially, in case you haven’t already seen it, we recently released a new version of Ping-Viewer. It’s got some nice visual/usage improvements, but also fixes a bug with flashing the Ping1D, so is useful for updating the firmware. That does still require the ping to be detectable though, so is more useful once your current issue is fixed