A similar problem was posted last year. There is an issue with older versions of sets on new software. 'BLF' functionality on internal auto-dial keys is lost with these older version sets. Similarily, if you were to have 7310 sets with the actual BLF snap-on module, the add-on will no longer work. The problem is the same with any type of set 7208, 7310, 7324. A real quick indicator is to use the contrast adjustment [F]*7. If the set will only go to a maximum of 4 contrast settings, it indicates an older version of the set which will exhibit this problem. These older sets are also incapable of 'Use Set Volume' in System Programming - Feature Settings.