Hello, thank you for your response. We have indeed been using the arduino leonardo, with the shield directly on it, and still getting the same error. 

Thank you for your response! 

I actually have the URM14, not the URM15 so I tried the wiring you were recommending but the sensor was powered by a power supply (12V) instead of the shield. 

I also changed all the ‘’Serial'' instances by ‘’Serial1'' (is that what you meant?). I no longer have uploading issue. 

However, the serial monitor is showcasing white squares instead of the distance. My baud rate is 9600 on the serial monitor, and it is the same in the void setup() function. Any idea on how to approach this?

Here is my code (wont let me copy paste it all):