I’m no electrician (plenty here that are) but you’re measuring the voltage on an open circuit ... and not under load.
(a car battery will often show a healthy enough voltage across it’s terminals, but when asked to crank will go phzzt.
Or consider connecting your multimeter to your battery via two hair dimension filament wires. Yea, you’ll prob see 13.6 volts whatever, but these two wires will never deliver the power necessary to drive lights / coils / whatever.)
When the points close, a couple of amps (/ coil) is needed, and if the circuitry (switches / looms / bullets) are in poor shape then you will not get the power needed (volts x amps) to feed the coil(s).
... which is why I suggested you hot wire the coils directly to the battery.
Good luck Gary, let us know the eventual answer. Oh, and a belated welcome to this great forum.