Apple sometime ago implemented and released a completely new version of AirPlay called 'AirPlay2'. In theory iTunes etc. is supposed to be backwards compatible and retain compatibility with the original version of AirPlay.
I would advise doing the following.
- Check for and if possible update the firmware of your Pioneer receiver, not only have a number of brands and products added AirPlay2 support via this approach but it may fix some original AirPlay compatibility issues
- Check for and install any additional iTunes updates, I believe when Apple made this original change they did cause problems with AirPlay1 support and hopefully newer iTunes version have improved this
Note: I am referring to iTunes predominantly since this is the iTunes forum. If however this relates to purely Mac and iOS streaming and not iTunes then obviously the iTunes suggestion will not apply. In this case you still need to look at possible Pioneer firmware updates but any compatibility would more likely be down to Mac or iOS operating system updates rather than iTunes itself.