HP laserjet color M400 m475

Hi Guys

I have a customers thats about 200km away from here. His problem is when he tries to send a fax he gets a service error 409 and then the machine resets. I have helped him to update the firmware over the phone. i have not seen it happened. I am going on the work of the customer. I can not find anything in the service manual about a error 409.

Any ideas??

Thanks