My iPad, iMac, and an iPhone Pro 12 can connect to my AirPlay device without a passcode, but my iPhone Pro 11 prompts for a passcode

I am able to access my AirPlay Moon Ace amplifier from all of my Apple devices (iPad, iMac, friend's iPhone 12 Pro on my Wifi Network), but when I try to connect from my iPhone 11 Pro I get the following dialog box: 'AirPlay Code Enter the on-screen code for "Moon Ace".' My iPhone doesn't prompt me for a code and I can connect to my amplifier if I'm streaming music from the Apple Music application to my HomePod and then add the Moon Ace as a secondary speaker. In this case, the Apple Music app shows the connection as HomePod -> Moon Ace. I have reset my network settings on my iPhone. All advice is appreciated.