Custom ringtones not working

Hello fellow Ionic developer!
I want to custom ringtones and using [cordova-plugin-native-ringtones], i added a mp3 file to assets/ringtone.mp3 and my code :
this.ringtones.playRingtone(‘assets/ringtones.mp3’).then(data=>{
console.log(s);
}).catch(e{
console.log(e);
});
==>this one not working (and show a message : Can’t play the ringtone!)
Please help me!
Thanks.

Dear ionic team!
Please help me !