Pretty sure you need to select a MIDI channel for the Triton vst... The midi clips that you are "pasting" have midi channel information in them and most likely you do not have an instrument on that channel in the Triton vst and that channel is different than the channel info of the note events you inserted with the tool... The Roland JV 1080 vst will respond to any midi channel info so it will play the notes you inserted and the notes that you pasted even though they are on different midi channels...
Open up the "Inspector" on the left hand side of the screen... Select MIDI in the track strip at the bottom of the screen, Audio is selected by default... Go up to the MIDI section just below the FX rack, the channel will be assigned to None by default (top button)... Set it to MIDI channel one as this is the channel that you put the instrument on in the Triton vst... All of your notes should play now as the MIDI track for your instrument track is now transmitting on MIDI channel 1 and the Titon vst has an instrument on channel 1...
With None selected in the MIDI section of the track Cakewalk will respond to what ever midi channel info is embedded in the midi events, which could be multiple different midi channels...
