Unable to receive earpod toggle button event

EarPods toggle button event has been received on iPhone 7. But it hasn't happened since yesterday. The source code has never been changed.

The source code is roughly like this.

[[UIApplication sharedApplication] beginReceivingRemoteControlEvents];

MPRemoteCommandCenter *commandCenter = [MPRemoteCommandCenter sharedCommandCenter];

[commandCenter.togglePlayPauseCommand addTarget:self action:@selector(onTogglePlayPause:)];



commandCenter.togglePlayPauseCommand.enabled = 1;



- (MPRemoteCommandHandlerStatus)onTogglePlayPause:(MPRemoteCommandHandlerStatus*)event {
	 NSLog(@"toggle event! - never called....");
    return MPRemoteCommandHandlerStatusSuccess;
}

env

iphone 7 (ios 15.2)
xcode 13.1

How do I get this event?