How do I enable AirPlay on my MacBookPro?

I am using a MacBookPro mid-2012 running Mojave 10.14.6.

I am try to use AirPlay with my Vizio M-series TV.

My iTunes version is 12.9.5.5.

The AirPlay icon no longer appears at the top of the screen at startup. It used to.

I can get it temporarily by going to /System/Library/CoreServices/Menu Extras and opening Displays.menu, but it disappears within one minute and does not list my TV when I click on the icon.

When I go to Displays in system preferences, I am unable to turn AirPlay on; the only option offered is "off".

I would also like to use AirPLay with my iPhone 8 running OS 14.8.

Thanks for your help.