Hello,
I found similar topics about my issue but I cant really understand the solutions described 
I have my Octatrack running with an external synth.
on the MIDI track, I have setup the Track one to send midi notes to channel one…
if I press “PLAY” the midi notes are not played
if I however play with the chromatic mode (I put the octatrack as a keyboard) then my external gear works!
why can’t I play midi notes recorded into the midi sequencer of my OT?
Big thanks!
one random thing to try is check octatrack’s midi clock send and turn it off. one of my external synths was weird and wouldn’t play notes when it was receiving clock from OT.
Have you accidentaly placed one of the other midi tracks in solo mode? I went through something similar and wondering if that could explain it.
I could use the OT or an external keyboard to trigger an external synth (in this case, A4 and iPad) when I was on the active midi track that I wanted to use. I’d then be able to record the midi pattern as I saw fit but once playing back no sounds were played. I was going bonkers trying to sus it out until I realised I had solo’d another of the OT tracks.
Just have to check,
you hit yes, or clicked the pot after selecting channel 1 on your midi track?
Have you turned off the midi channels of your audio tracks in project menu?
There might be conflict with the audio track who own channel 1 to 8 by default.
you got it!
grr. I put the track in SOLO mode … grr I stupid!!
Big thanks !!!
I honestly must’ve spent the best part of an hour working out what was wrong about two days before you posted! Glad you sorted it. I disconnected/reconnected everything about a dozen times before spotting it!!!