[Rail Jon Rogut]

Dana

It sounds like you're doing everything right.. Do you have anything else inserted on the master fader when you try and plug-in an I/O insert on the master fader?

A work around to try - which would place the compressor pre the master fader which is better anyway - assign all your mix tracks to a pair of busses instead of outputs 1&2.. create a stereo Aux track and assign its inputs to the same pair of busses.. assign the output to your stereo out 1&2. Insert I/O insert across the Aux track and see if that helps.

Rail