Sorry about that.
The specs on the Layen 4.0 says it has AVCRP protocol (which is what allows BT connections to control the player), so I just assumed it would work. However, after reading your responses here, I took my Layen BT receiver out to the Spyder and tried it. And I got the same results you did - even with the Google Music app which CAN be controlled by my Sena SMH10 headset. So I'm wondering if that is an error on the specs listing for this unit. Also with the Layen BT receiver plugged in to the Spyder, the multi-function display on the dash kept alternating between "iPOD" and "AUX" as if it couldn't decide which it was actually connected to.
Well, at least they have good customer support, as shown by their quick response to you, and an offer of a refund.
That said, the handlebar control will control the volume, and if you have a mount for your phone in the cockpit, then you can use your phone to control any app, including Pandora, and feed the audio into your Spyder's entertainment system using the Layen unit or a similar unit. (Of course I realize you can do the same with the other BT receiver you already have.)