If the Fi light doesn’t blink at all , then i would remove the tank and get access to the harness where it connects to the dash & also the right kill switch block, clean up the pins as much as you can to make a very good connection at the front and even behind the dashboard.
Also the dashboard has a “mini” harness that joins the “main frame” harness , start from the dash going to the harness = the RED wire is what turns on the LCD glass.
Open the dash unit and look for signs of damage.
The RPM tacho (RPM needle) must go UP then down , as soon as you turn the key on ?
Then also go to the ECU, disconnect the plugs carefully (it could be a 2plug ECU or single plug ECU = 650 has had multiple ECU changes over the years by Hyosung until settling down with Delphi ECU) -> The connections to the ECU play a critical role too.
Update us with your progress until then.