Check the system status - there might be a problem at ECMWF end.
Check your ftp is not full - one of the most common reasons that dissemination fails is because there is insufficient space for the data on the recipients disk.
Check whether there have been any changes to the settings/passwords/permissions which control access to your disk.
See - ECPDS (ECMWF Production Data Store) - the system used for transmitting real-time forecast data to users (note: it is only available to Member & Co-operating States/Full NMHS/max-charge customers). With the ECPDS you can try:
checking the status of your real-time forecast data dissemination