The AE-1's hotshoe won't fire the flash from some reason. I have the shutter speed set to 1/60s and my aperture is set to A (auto). The test button on the 155A fires the flash as does shorting two of the hot shoe connectors, but the shutter button won't for whatever reason. I can see that the camera senses the the flash because the light meter is locked on the appropriate f-stop. But I have no luck getting it to fire the flash. Using the sync port on a different, non-hotshoe flash unit works but I have no way of testing a sync port on the 155A. I've also tried cleaning the hot shoe connections.

Any help would be appreciated.