RESOLVED.
FYI…
I used solutions based on info from these 2 people:
aihodge & mbaker ---- Thanks!
(It’s an update from an old thread I started, but the solution probably needed to change years later because of Unity updates) How do I get the audio running in background (iOS)?
SOLUTION:
At the bottom of the startUnity() method I put this code:
[[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlaybackerror:nil];
[[AVAudioSession sharedInstance] setActive: YESerror: nil];
[[UIApplication sharedApplication] beginReceivingRemoteControlEvents];