Bug Ios native app audio get muted on switching other engine games to unity games from 2nd times

my native ios app contains cocos 2d, cocos creator and unity games . so when i open and close cocos game then open unity game , audio is working fine but when open cocos game again then unity game this time audio. get muted . I have to close the app and restart again to get audio back .

am using unity 20019.3 for my project , there is an issue in my unity game when our device is connected with bluetooth headphone , instead of audio coming from headphone it comes from device speaker so to fix that issue have added this code in UnityAppController.mm startUnity method .

[[AVAudioSession sharedInstance] setCategory:AVAudioSessionCategoryPlayAndRecord
withOptions:AVAudioSessionCategoryOptionAllowBluetooth error:nil];
[[AVAudioSession sharedInstance] setActive:YES error:nil];

after adding this code , when i switch between cocos games to unity games audio get muted in both cases(with and without bluetooth headphone). not able to find the issue , so anyone can help for this issue .

thanks in advance