I have a couple of suggestions.
First, make sure the format is located in a library that is in your format search path (FMTSEARCH option). By default in EG, this is something like (WORK EGTASK SASUSER LIBRARY). You can check PROC OPTIONS OPTION=FMTSEARCH; to see what the current setting is for you.
Next, EG maintains a cached list of formats that it gathers from the SAS server. To make sure that your new format has a chance to be detected, go to Tools->Options->Data: Data General, and look at the "SAS Formats/Informats Cache". If the button is enabled, click "Clear cache". It will be enabled only if you have already used EG to browse the list of available formats during the current EG session.
Chris