I recently updated my max2player player/server with IQAudio AMP Card and now when trying to adjust volume with any squeezeplayer android app nothing happens.
When adjusting the volume with Alsa mixer it adjusts the volume fine but obviosuly this is not a solution.
Please make sure your command line options are set correctly. They should define your sound card as hw:1 or hw:0, depending on which slot the IQaudIO card occupies on your Pi (check debug info on Audioplayer menu to find out at the bottom).