airplay displays off - no option to turn on
I am trying to set up the ability to connect to airplay via the top menu bar.
Considering what is written below - what else do I need to do to add the ability to connect to Airplay via an icon in the menu bar?
I am running Mojave.
I have gone into system preferences>displays.
I have ticked the box that says 'Show mirroring options in the menu bar when available.
However the drop down menu within system preferences>displays says that Airplay Display is OFF and does not have an option to switch it on.
There is an airplay device on and available.
When I go to System Preferences>sound the existence of an airplay device is confirmed