When I got home from work, I went to the rain sensor and took it apart. I wiped it down best I could. The little discs inside were swollen.
The Iro immediately posted a device update of "Rain sensor deactivated" when I took apart the sensor. I put the sensor back together and the "rain sensor activated" message was immediately posted in the device update.
I took the cover off the Iro. A message was posted that said, "Device status power cycle."
I checked the wires leading from the sensor to the Iro and they looked fine. I removed the wires from the R1 & R2 terminals, cut off about 1/2", stripped about 1/4" of the plastic off, and reinserted the bare wires into R1 & R2. See photos below.
I put the cover back on and let the Iro reconnect to the wifi.
The device status of "Rain sensor activated" displayed again and has done so every 2 minutes.