Occasionally it may not be possible to open/close the front end using the front end application (idappli). You may have message which says for example "lost connection to device server". The EHO (call 25-25) can usually help with this matter. On ID14 this problem is usually observed the day after a machine day and the normal fix has been to switch off and back on the Safety Shutter PLC in CC0 (NB only do this if you know what you are doing). The EHO also knows how to do this if you are not sure.