I would verify that your getting power to the distributor before doing anything else. After that we need a little more info, I assume this is an Hei distributor? If so you need to make sure your getting a full 12 volts to the distributor. Approximately many miles on it? I’d pull the cap and make sure the cap and rotor are in good shape as well as the coil and connections. You can ohm the coil out to make sure it’s still good. If it is indeed an Hei, it’s a pretty simple system and with a little more info not hard to trouble shoot.
Here’s a video showing how to test the coil
https://m.youtube.com/watch?v=SEOdRoeS4mk
Edit- I didn’t type quite as fast as tdangle...