AirPlay no longer works for third party devices
I am using iTunes on a Windows 10 PC. My AirPlay device is a Denon DNP-720AE which has worked well for several years streaming my ALAC music out of iTunes to the Denon streamer using my iPad 4 and the Apple Remote App. With the recent release of the latest itunes 12.9, I no longer can stream my music as before. I have checked for firmware updates from Denon and none are available. When contacted Denon support they point the finger back to Apple. When trying to connect to the Denon unit I receive the following iTunes error message:
"An error occurred while connecting to the airplay device “DENON:[DNP-720AE]”. An unknown error occurred (20)"
Is Apple now blocking third party hardware from using AirPlay to promote it's own products? Has Apple stopped supporting third party hardware for use with iTunes and AirPlay? Did Apple make AirPlay incompatible with legacy devices. Is AirPlay2 backward compatible with legacy non-Apple devices?
Please advise a solution or confirm my thoughts above.
Windows 10, Windows iTunes 12.9 AirPlay