Unfortunately recently I'm having the same issue of no spark coming from coil at random times mostly when car is parked overnight then in morning it refuses to start.
All electrical have been checked like ignition coil, distributor pickup coil, timing advancer under dashboard is plugged into white socket, new distributor cap, battery is new, plugs and plug wires new and other electrical connections have been tested for continuity.
Once car is started after lots of fiddling with plug wires, connectors etc. then rest whole day it will start and run just fine. It seems there is no resolution to the problem but is there something I might be missing in the diagnosis?
I've also experimented to create spark by removing the distributor from housing and keeping the electrical connection connected then rotating manually by hand, then in this case I get spark from the coil and can also hear the fuel pump engage. But when cranking the engine there is no spark.