On the working master, if there are no extensions connected to the removable faceplate then its pretty easy to say thats why the others dont work.
You can connect two extensions to this master faceplate (thats all the IDC jaws will cope with). Daisy chain more if you need them.
IMPORTANT Extensions can affect the speed of your broadband. So only connect pins 2 & 5 and remember that phones at the extensions all need microfilters.
An ADSL faceplate may be a neater solution especially if the ADSL modem can be connected to the master socket