To show what Pandora, Spotify or any app is playing (and play, pause and skip it), Android needs to give ByteFall Viz notification access. It reads no notifications, only what's playing.
Switch grayed out? Android holds it back for apps installed outside a store: open App info, tap ⋮ top right, then Allow restricted settings, and try ALLOW again.
SOURCE — AUTO hears the other apps directly where they allow it, and through the microphone where they don't (Pandora is one that doesn't). OTHER APPS: only directly. MICROPHONE: only the microphone. SCREEN AUDIO (a computer's browser): the sound of a shared tab, or on Windows the whole computer's. Tap the left or right edge to change style; the middle shows or hides the controls (on a computer: ← → change style, F full screen, H hides the controls).