I figured it out. "User error"@Xhorder
Normally you should see a persistent notification for as long as the app is running.
If media is playing, this notification also show playback controls.
Do you have this issue only when the tablet is displaying the lockscreen or also if fully unlocked ?
Lockscreen behavior may vary between Android ROM and versions.
Notifications were blocked, although I don't remember doing that.
Thanks, working fine now.