Targeting S+ (version 31 and above) requires that one of FLAG_IMMUTABLE or FLAG_MUTABLE

[OmarLkhalil]

if you are on S+ android api you may get this error so in notification helper you can update pending intent to check if current sdk is higher than S api

val pendingIntent: PendingIntent = PendingIntent.getActivity( context, 0, intent, if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.S) { FLAG_IMMUTABLE } else { 0 } )