Hi,
If you connect your Tabled Using Cast it will exclusively use Cast and you could not Recast using MMA ⋮ -> Cast to as Chromecast will not be available then.

Try to restart Tablet, Start MMA and then try to cast to within MMA?

Which version of MMA and what file type(s) are you trying to play?

Can stream to chromecast audio from BBC Sounds, Spotify but not Mediamonkey. The casting icon appears, my tablet will connect to devise but the Mediamonkey will not play.