airplay disappeared from my tv, but not my sons. how do I get it back?

if you're doing something like playing music using an Apple TV along with airplay speakers.. something changed in the recent 16.2 tvOS update. The airplay option to select other HomePods is no longer shown in the upper left of the Music app's Now Playing area. You have to hold down the TV icon on the remote and Control Center will pop in from the right (not sure if that's a new feature or not, it's new to me). From there you should see an icon that shows what speakers you're connected with. tap on that and you'd get the list of airplay devices that you can check/uncheck etc.

You can also go to the Settings app > video and audio > audio output and assign a default audio output and add temporary ones at the bottom, which will bring up that same checklist.

This same thing can also be done using your iPhone within the Home app, but it's a bit harder to describe how to accomplish it from there.

if that's not what you're referring to, then as Rudegar has indicated, not enough information has been provided.

using the appletv box?

from what device do you attempt to airplay?

if not an appletv box then what tv?

elaborate