Is not executed? Or never returns? Big difference.
The MUX shield has an LED on pin 13. Is that LED lighting up? Pin 13 is one of the SPI pins that the Ethernet shield uses.
I added an SD card to the ethernet shield and now it is both executed and I receive some smiley faces (which i don't understand why) on my command prompt (where I'm using node). However, the loop still doesn't work. So it only goes through ONCE. After that my sensors get deactivated. By that I mean, my sensors have two LED's on them. One is red which is the power, and one is green which lights up only when it detects an object. After the loop is executed once, the green LED's never light up again unless I restart the shield or unplug the USB cable and plug it back again.
And my MUX shield only has one LED which is the Power LED.