On the surface, when querying the API, it seems enabled
> a = navigator.requestMIDIAccess({sysex: true})
Promise {<pending>}
> a
Promise {<resolved>: MIDIAccess}
{__proto__: Promise
[[PromiseStatus]]: "resolved"
[[PromiseValue]]: MIDIAccess
{inputs: MIDIInputMap {size: 0}
onstatechange: null
outputs: MIDIOutputMap {size: 0}
sysexEnabled: true
__proto__: MIDIAccess}
}

(I have not actually tried using it)

Do you get different results from the API itself?

My connection is very similar, however, I call it on window.load:

window.addEventListener('load', function() {        
if (navigator.requestMIDIAccess({sysex:true})) navigator.requestMIDIAccess().then( onMIDIStarted, onMIDISystemError );
});

function onMIDIStarted ( midi ) {
          console.log (midi);
	  midi.onstatechange = midiConnectionStateChange;	 	   	 
	}

midi returns : 

inputs:MIDIInputMap {size: 4}
onstatechange:ƒ midiConnectionStateChange( e )
outputs:MIDIOutputMap {size: 4}
sysexEnabled:false
__proto__:MIDIAccess

navigator.requestMIDIAccess({sysex:true}) returns a promise (so your if-condition always returns true, for MIDI supporting browsers and an exception for non-supporting browsers) and you end up requesting MIDI access without sysex: true, so I am not sure your code is correct...
I think you need to check whether navigator.requestMIDIAccess exists and if so, call it with sysex: true -
if (navigator.requestMIDIAccess)
{
  navigator.requestMIDIAccess({sysex:true}).then(onMIDIStarted, onMIDISystemError);
}

Also, I believe Web MIDI in general requires HTTPS (and did so from the beginning), whether you ask for sysex: true or not.

I just ran your code from the console and I do see what you get back from a = navigator.requestMIDIAccess({sysex: true}); 

I was looking for it in the onMidiStarted callback in the midiAccess that gets passed to it. Is this normal ? I would have expected the sysex value to be passed through as well ? 

I will try and change up the code to midi=navigator.requestMIDIAccess({sysex: true}); and ignore the midiAccess that gets passed to onMidiStarted for now. Will keep you posted.

No, you are correct, only sysex: true requires HTTPS.
http://sites.google.com/a/chromium.org/dev/developers/design-documents/web-midi

No, midi=navigator.requestMIDI... will not work as you expect, because in this case, midi will be promise, not the WebMIDI object. onMIDIStarted should get the WebMIDI instance as the midi parameter (in your code) and the WebMIDI instance should have a sysexEnabled property.

*will be a promise

The code and the result I showed in comment 3 is from the console, after expanding the internal [[PromiseValue]] property.

Huzzah! we have liftoff! I've got it up and running in sysex mode with full rgb. Thank you so much for your help! 

I am glad it worked.