I used to have a moped that would not run if the headlight bulb was out because they were on the same circuit. In fact, there was a toggle switch on the underside of the headlight housing that allowed me to bypass the bulb in such situations.
The electrical harness on the Tao Tao is, undoubtedly, more complicated since it includes a battery and starter. Just for the heck of it, though, check your light bulbs.
...Operating with impunity in the legal gray area between bicycles and motorcycles....