Your Bravo probably has a single light bulb with a dual filament inside the bulb (one ofr tail light, one for the brake light). Some newer Bravos had two separate light bulbs for tail and brake lights.
To check it, remove the two long screws from the red plastic tail light lens and remove the lens. Now gently push the bulb in and twist till it releases and then wiggle or pull it out.
Hold the bulb up to the light and you should see two filaments inside the bulb. If one is missing or broken that is why your tail light (running light) doesn't work. If the filaments appear OK, then polish the metal end of the bulb contact with some light steel wool (0000) grade. Also get some electrical contact spray and spray that into the socket where the bulb goes. Sometime the electrical wiring and components on these old mopeds get corroded and need to be cleaned to work properly.
You can use a GE 1154 6 volt dual filament bulb if you need to replace a defective bulb.
You may also need to clean the wire connectors and ground wire on the back of the tail light assembly but try the bulb test first that's a bit easier and hopefully will fix the issue.