Throttle Below Failsafe error message

I’ve got an IRIS+ running 3.2.1. The phone I’m using is a Sony Xperia Z running Android 4.3. I’ve created a mission in Tower, connected to the IRIS, set waypoints (altitude and duration), and then uploaded the mission to the IRIS.

When I then push the “arm” button, I get the following message:

ARM: Throttle below failsafe

I’ve searched on that error message and get nothing. Any thoughts/suggestions?

I believe I answered my own question. I thought (erroneously) that all command functions could be done from Tower. Then I watched the video on using the remote first, then switching to “Auto” and making the Phone/Iris connection.