Had this exact issue and hadn’t found an answer that resolved. Tested on other Roku device and everything worked. Went back to the problem Roku and went to settings>system and reboot the Roku and airplay started working in full screen again with audio.
Hi @SloSixty6,
Thanks for reaching out to the Roku Community.
We'd like to know more about how we can help. Could you send us a screenshot/photo that displays what is happening on the screen? And walk us through the step-by-step on how to reproduce the issue. Lastly, may we ask when did you notice the issue started?
Let us know on what you find out.
Regards,
Nimfa