If your track does not have adequate power supply to the locomotives, then the DCC signal won’t get through either.
Take a quarter or screwdriver blade and go around your layout creating electrical shorts by laying the quarter/screwdriver blade across both rails every 10 feet. Your Digitrax system should shutdown when the short is present. When the short is removed, the booster should return to normal operation. If the unit does not see a short or it does not return to normal operation after the short is removed, then you need to add more feeders.