I came across the same problem ages ago, but with the ProChannel FX Chain enable/disable. The automation would not work unless the ProChannel in question was open (I think it worked if the PC was open on the console). Cakewalk replied on the forum that they were aware of this limitation but that fixing it would break a bunch of other stuff, so there was no fix planned. I don't know how they feel about it now.
There is a similar problem with the arpeggiator on/off - automating it does nothing unless the track it's on is in focus.