Is the distributor tight? The little known secret about the evident simplicity of Pertronix is that the electronics module MUST be grounded and if the distributor is loose in the engine, it might not be getting a good ground.
Basically there are only two wires --- red is hot and black is coil NEG. Black is NOT ground
Hook RED to switched 12V --the "key" side of the ballast. Of course the ballast and coil both must be good. You can easily check the ballast for continuity, but testing a coil is really not conclusive.
Make sure that the coil NEG is not getting grounded. This might happen, example, if a tach wire is also connected and the tach is bad, or the wire shorted to ground. Make sure the external radio suppression cap on the coil is NOT connected to the black/ coil NEG.
Obviously, make sure the distributor is actually turning. This might seem obvious, but there have been cases where the cam, cam gear, breakage in the distributor, etc, have stopped rotation when the rest of the engine was cranking over.
Some systems draw excessive current with the key "on" but with engine not turning and some do not. Pertronix, Mopar ECU and of course breaker points all do. GM HEI, example, does not. So if it's been left sitting for awhile, key on, the module, coil, or ballast may be gone.
