This message is telling you that you already have the Liquid Rhythm Max for Live device running and you are trying to run the VST or AU plugin at the same time.
At this moment you can only have either the Liquid Rhythm VST / AU plugin or the Max for Live device running at one time.
We are hoping to offer more flexible workflow possibilities in the future, but as of the current version, you must restart Ableton Live if you have been running the Max for Live device and you want to use the VST or AU plugin right after.