Hi @Josh1977, welcome to the forum! 
This is usually caused by having the RX and TX wires the wrong way around, or from the serial baud-rate being incorrect between the Arduino and the Ping device. Can you confirm which Ping1D firmware version you’re using? It’s possible our guide and/or code are outdated - I’ve asked internally and am trying to find out what the latest information should be.
In this recent thread I connected successfully to our latest firmware (Ping-v3.28_auto) by changing the baud rate from 9600 to 115200 (e.g. change from pingSerial.begin(9600) to pingSerial.begin(115200)), which you may wish to try. Otherwise you should be able to roll back your firmware to Ping-v3.27_9600 using PingViewer (as specified in the guide you linked to), after which the example code should work as-is assuming your wires are connected to the correct ports.