Airplay audio asks for a password

HI there JK-2020,

We'd like to help answer your question as best we can.

From the details you provided, along with what's showing in the screenshot, this is going to be a question best asked by the manufacturer of the amplifier you're attempting to use as your iPhone is asking for the passcode to connect to it via AirPlay.

Take care!

Hi JK-2020,

As you've already contacted the support for your amplifier, and they recommended to contact Apple Support, then that's the next step.

You can reach out to Apple Support using this link: Get Support

Cheers!