F100 not showing frame numbers

Hi folks. I bought a used f100 last year and I'm just getting around to using it. I think it's a dud, and I hope I'm wrong.

I use f80 as my main 35mm camera for over 12 years and recently the last of three died. So I dug out the f100 and just ran a roll through AFTER resetting to factory settings.

Problem: It is only showing frame #1 even though I can hear the mirror and exposure and film advance.

I open up the back and sure enough it's going through the film.

I am hoping a Nikon guru can point out some obvious thing I'm doing wrong. I'd be eternally grateful to be pointed in the right direction.

TIA!!

Hi. I use an F100, but have not encountered this problem. There is a multiple exposure setting. This would cause the shutter to fire, but would keep the counter at #1. Check that first. It's on the the top left dial. It should be set to 'S'. No other setting should cause that behaviour.
I hope you get it fixed. It's a great camera.
Alex