I have two MultiPlus 12/3000/120 in parallel connected to a CCGX controller. After using either the controller or the power button on the front of the unit to turn off the Multiplus to turn them back on you must first use the controller or power button, but then you must unplug and replace the communication cables, in the correct sequence. Until you do that the units remain dark and unresponsive. You must first unplug the slave and once the lights start flashing you plug the cable back into place, then unplug the master, wait for flashing lights and then plug in the cable again. The units them work well until the next time that the power state is changed.
Of course the problem with this is that I must leave the cover off of the Master so that the cables are accessible and reaching into the unit is potentially a shock hazard.