I have had the same issues with my 6ex and trainer/simulator stuff I had no input whatsoever just like you describe. I finally figured it out. The cords do not fit correctly although it looks like it does. My brother was frustrated and pushed VERY hard into both plugs then presto it worked great.

The final fix was to heat the plug on my cord a bit and fit it on the tx ,it expanded a bit and now works great. I hope this helps.

(edit) these were not futaba cords they were GWS but it was the same symptom exactly.