Ok, I have an '82 Seca (DOHC, should be very similar to yours) and I had a lot of electrical issues similar to you, where there would be no spark on either side that would come and go. Same issue, when the cranking would stop/killswitch would be stopped I would see a spark.
A few questions first: Was this bike running fine before and then suddenly stopped, if not then are you missing any big pieces like the TCI, coils, etc.? Have you tested to see if the coils are in spec, checked the pickup coil resistance, changed out the spark plugs, and looked for loose wiring? There is a circuit diagram in manual posted in in the garage forum that is for the DOHC bikes (if it's an '82 Maxim) that has a troubleshooting guide with specs. Once you've done all that, then I would try the next few things.
Bypass the side stand relay switch by unplugging the black/white wire that goes into the TCI, it's the black box with a red plate that says "IC Ignitor" on the left hand side, maybe under some paneling for you. Commonly the switch on the stand can go bad. If that did not help, try bypassing the neutral safety relay, mine went bad very recently. For that one, you'll need to find the black relay under the tank that looks like the attached pictures, should have two red/white wires, a sky blue wire, and a black/yellow wire going into it. There is a section in manual for the starting circuit that details how to test it, but it's easier to just connect the red/white wires in the connector with spare wire and see if it will start. If that fixes it, just twist the red/white wires together for a more permanent fix and tape it.
If after ALL of these things it still doesn't work, then your TCI box is likely toast. They don't make them anymore, so they are going to be in the hundreds of dollar range IF you can find a second hand on on ebay or elsewhere. I have also seen people attempt to repair them by re-soldering all the connections and replace broken circuit pieces, but it's pretty difficult if you are not used to electrical repair. You could try to get a local place to fix it for you, otherwise your last option is this czech ignitech.cz shop, but in the current COVID-19 crisis, it might be very difficult to get anything shipped to you. I believe the user djsky96 got that system working for his bike.
