No info on negative when using flash
I'm using an Olympus OM-1 manual 35mm camera with a Sunpack Auto140 hotshoe flash and I'm finding that any shot I take using the flash doesn't turn out, and I am sticking to the exposure guide that is on the back of the flash for every shot, and always using a shutter speed of 1/60th. When I develop the negatives the frame is blank. By "blank" I mean there is no information whatsoever––there is nothing in the frame on the negative and it is totally black when I make contact sheets and therefore I know I'm not overexposing the image with the flash because it would be white on the contact sheet.
I'm wondering if this is a mechanical problem. I hear the shutter and see the flash trigger when I press the shutter button, yet no image. The camera otherwise works perfectly when I am not using a flash.
Any insight would be appreciated.