When it appears “Not allowed to connect while connect/disconnect is pending.” it will no longer be able to connect

System.InvalidOperationException: Not allowed to connect while connect/disconnect is pending.
在 MQTTnet.Client.MqttClient.d__42.MoveNext()
--- 引发异常的上一位置中堆栈跟踪的末尾 ---
在 System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw()
在 System.Runtime.CompilerServices.TaskAwaiter.HandleNonSuccessAndDebuggerNotification(Task task)
在 System.Runtime.CompilerServices.TaskAwaiter`1.GetResult()

what‘s the reason,( _mqttClient.IsConnected is false) thank you

Start by reading the MQTTnet.Client.MqttClient.ConnectAsync stack-trace entry and trace how its connection state is checked around the reported exception. Reproduce the reported condition if possible and document the specific sequence that leaves IsConnected false while connect/disconnect remains pending.

Written by the indexing model from the issue text.