It’s probably a similar hardware-level issue as discussed in this thread for various other gear: Pyramid incompatible with M-Audio?
The short version is that either the Medusa is low on power to transmit sufficient voltage on the MIDI line, in some cases powering with external power supply instead of USB has helped. Or there’s a hardware-level incompatibility (which shouldn’t exist, MIDI being a standard…) that can be worked around by adding a MIDI-thru box or similar.