I had an issue with the blinkers not canceling. They worked but didnt cancel. I know yours dont work at all but I just thought it may be related somehow or give some insight. On my 97 there was a blinker cancel module that had a contact switch and a black electrical box. Located in the steering column. I tried to clean it, and finally decided the electronics were bad. I replaced it and it worked.
At the same time I was having the A/C control fixed by e repair. I sent the blinker switch in with it and he looked at it and fixed it. I never installed it, but he said some capacitor or something was bad. Maybe, its possible for this to completely knock out the blinkers. Doubtful, but I thought I would share the info. Best of luck. I would listen to others first as they are way smarter than me with the NSX!