At this point, not sure what your comfort level is? I would pull of tank and unplug all JST plugs - to handlebars-etc
Sounds like either you have a short or bad computer.
Then would plug one in at a time - plug in -= unplug - go top next - until you see what works-doesnt. I found 2 shorts in mine - one from tach ring that melted entire way back to connector under tank, and another i found with turn signal wire.
Both these direct shorts impact other components and make you chase your tail.
All I can say is if you know how to take the bike apart - use volt meter - then unplug all and plug back in testing one at a time - headlight, turn signal, turn signal, high beam, brake lights, tag light - until you find one that doesn't work when it is the only thing that is plugged in - then ohm out why??
Did computer send 12v - is there ground??
Just my opinion