@Zach pointed me in the right direction. One of the pins on the header was bent... The bottom right one. The installation is working now...
Now I have to figure out why the Iro set the zones to such long watering times. Seriously? 1.5 hours on a zone? Maybe I was doing something wrong before, but it was getting 15 minutes 3 times a week, not 1.5 hours every other day.
Thank you for your help!