I have no knowledge of the Sena 10U, however, try this :
Start afresh by deleting ALL Pairings from the Trophy and your Sena.
Forget about connecting anything else for now.
Pair the Sena to the Trophy as HEADSET 1 using the option on the Sena
( if there is one ) to Pair as a MOBILE PHONE.
Once that is done, test to see whether you receive Audio from the Trophy to your Sena,
having made sure the Trophy is set to Output to HEADSETS and not Speakers !
If that works, then move on to Pairing your iPhone as DEVICE 2.
If it doesn't work then there would appear to be a compatibility issue
between the Trophy and your Sena. ( Gut instinct tells me that's unlikely though ! )
Cheers

