Hmm,
I've probably steered you wrong. In order for the IR receiver to work, it needs a source of power, a ground, and a signal lead. A stereo plug has 3 connections and can supply all of those. If the pioneer receiver only has a mono jack then the source of power (5 volts or so) is missing, and it expects your IR receiver assembly to supply the 5 volts.

Of course it is possible to hook up a 5 volt power adapter, or pull the power from a HDMI jack, but that may be more than you want to get into.