I have the 20S Evo. Of late, it's been having an issue playing music from the Nav if there's a disconnect. I often have to tell the bluetooth to disconnect than reconnect...sometimes turn off the Sena and turn it back on. I dropped my helmet this year, and this has increased in frequency, but I also updated the Nav. Don't know if either of those created the issue.

 

Do you need it paired to the iPhone? Or for testing...
Starting with Sena OFF:
Turn off BT on the iPhone.
Turn on Nav.
Turn on Sena.
If it connects easily, the issue is that the Sena is trying to use the same internal BT channel for both iPhone and Nav, and the iPhone is being considered the "primary" device.
Now turn on the iPhone BT - it SHOULD stay connected to the Nav until the connection is broken (range to helmet or turning off the Sena or Nav.)
There are two possible quick solutions:
1) Clear ALL connections. Reset the Sena to factory, remove the Sena from both iPhone and Nav settings, then connect Sena to Nav, then to iPhone. This SHOULD set the priority to the Nav
2) Be sure to disable BT on the iPhone until nav and Sena are connected.

Harder solution:
If the Sena has the ability to select specific channels for phone headset vs nav audio, use them. This used to be fairly easy to do in the SMH10R (the last Sena I used), but I don't know about the current units.

 

@ChrisZ, I may be able to assist you. I upgraded from a Sena 20S to the Sena SRL, connecting to my iPhone & Nav VI. The transition from the old to the new SRL was so frustrating. Nothing in the setup guide or Sena support seemed to fix the connectivity issue. However, through trial and error, i found a fix.

So here's what worked for me:

• Clear all Sena-paired devices and clear pairing of Sena on your iPhone and Nav VI.
• Start new pairing procedure on the Sena:
  a) Pair your phone with Sena
  b) Pair your Nav VI with Sena as a second phone pairing, NOT Navigation/GPS

This should fix your problem (famous last words)

Here's another critical point:

When you first start out in the morning, have Sena and phone nearby and powered up before the Nav VI powers up, and everything should work seamlessly.

NOTE: i am using old firmware and haven't bothered with any of the updates.