We are authorities in production sound recording for video and filmmaking. Your other condenser mike of the same brand works perfectly, so you can assume it's not the Nagra. Running next door, you then try plugging the rental shotgun into the audio mixer of the video studio. To the professional soundperson, these terms are all too familiar.
Condenser microphones require a DC voltage in order to operate.
Electret condenser mikes require only a nominal supply of one or two volts, and this is usually provided by a small single cell battery inserted into the microphone head or connecting cable itself. Microphones intended for use in recording studios usually operate off of a 48 volt source, as where location mikes used to draw 12 volts. For example, Sennheisers are available in both versions. Not all manufacturers of condenser mikes use A-B powering, though. Phantom powering employs a different pin and voltage configuration.