This situation would be where sometimes you see that a customer has contacted the QueueBot, but the agents do not recieve any messages to take the customers request.
One reason is that all your agents are busy in chats, disabled, or offline. You can check this by using Option 2 of the Agent Options Menu. Agents who think they are listed incorrectly as 'Busy' or are listed as being in chats that they are not can use Option 14 to set themselves 'Free'.
Another reason for this is if your QueueBot is setup with the exact following settings outlined in red:
In this situation, every hour, the first chat recieved by the QueueBot will not go through. To remedy this, you can change the settings to the below. Note how the time indicated in the image below is less than the time in the image above. This is important.