I've seen many similar posts about this, but none match my issue precisely... so:
 
I have a MOTIF ES8 synth plugged into an M-Audio interface connected to my computer. I recently tried to record some MIDI after not using Sonar for a bit and it records fine but will not play back despite Sonar showing the notes in the track and indicating that they are playing. After trying all kinds of settings in Sonar and the ES8 I loaded an existing song with MIDI tracks. The existing MIDI played without any issues. I then tried to record a new MIDI track in that song and the issue of not playing back happened with the new track even though I mirrored the settings from the old track.
 
So it seems like Sonar isn't talking to the ES8 on any new recorded tracks, but does with existing tracks... anyone have ideas on what is happening? Please let me know if any other info would be helpful.

How is your routing? What is the output of the MIDI tracks?
When the playback is audible (the excisting projects), does it actually use the Motifs sounds, not the MS Wavetable, for example?
I assume the manual of the Motif tells whether the USB connection is able to transmit audio, or should it be connected
with an audio cable to transmit its sounds to SONAR.

Kalle Rantaaho
I assume the manual of the Motif tells whether the USB connection is able to transmit audio, or should it be connected
with an audio cable to transmit its sounds to SONAR.

According to the manual "The USB connection between the instrument and the computer can only be used for transfer of MIDI data. No audio data can be transferred via USB"

The Motif is set to USB for "midi in/out" and the audio is transferred via 1/4" audio cable from keyboard to interface. The playback does use the Motif sounds, I changed the instrument on the keyboard during playback to confirm this.
 
Note that the way i have it set up has worked flawlessly for however long I've had Sonar X3 (2-3 years now). I took a brief break of about a month or two where I didnt record anything and this problem has come up.

I'm still trying to figure this out but I'm down to trying very random things. I just turned on the tracks "arpeggiator" and it plays back...only its naturally arpeggiated. WTH??

I have anEX5R, so I'm familiar with Yamaha and how they do things. I'm away from my computer, so I'll try to "talk you down"remotely.first. turn local off so you don't double notes as you go in.Set up a midi track. Pick an input port such as USB ..
Pick a channel to receive on.Let's try channel 1 for simplicities sake. Pick an output port, such as USB... make sure you pick channel 1 as well. Now make sure that the patch you want to hear is set up to transmit and receive on channel 1. Now hit that blue button that will echo midi out on the track.Now, remember, midi is instruction for your synth, not sound.If you are going to monitor through your interface, you need to set up an audio track so your computer can route the sound coming out of your output. Set that up for the proper input and output selecting from the audio interfaces options in the menu for the audio track. Press the blue button so it echos the input. Finally, do you have something plugged in to the audio device on the output side? Headphones or monitors? I think I covered everything,but like I said, I'm away from my computer. I'll check this post later and fill in the blanks. It seems like a lot of steps, but it's really not many more than playing the radio. You do it a few times and it all comes back.

In the process of looking into your recommendations Orangesporanges I found that most of what you mentioned was tried... BUT it made me notice that there is a dropdown for IN, a dropdown for OUT, and just below that a dropdown for MIDIChannel... ends up changing the midichannel from "none" to one of the many "defaults" it fixed the issue.
 
In my defense I have never had to set that dropdown in the past, and my existing songs (where the midi works fine for past recording but not for new tracks) does NOT have the midichannel set to "default", its set to "none"...and I'd love to know how, when, or why that has changed when the only update I've done recently was Melodyne.
 
Thanks for your help folks, I appreciate it :) and thanks Orange for getting me to the solution.
 

Wasn't sure if it would do any good, like I said, I was away from my computer at the time ( daughter's gymnastics meet), but  figured a pseudo "step by step" would get us closer.A nyway, glad you can start making music ! Say hi to Space Synth Cat for me.