✅ Why breakpoint is not hitting?

await _mqttClient.Subscribe( subscription, OnReceived );

private async Task OnReceived( 
    IMqttClient sender, 
    MqttDelivery mqttDelivery )  
{                                                              
    var subTopic = mqttDelivery.Topic.Split( '/' );            
                                                               
    var addResult = TreeRoot.Add( subTopic );             
   
    if(!addResult)
    {
         // do smth
    }                   
}    

public bool Add( string[] subTopic )
    => Add( subTopic, Level + 1);