External Flash Only Fires Once

Weird problem – Setup is as follows: D5600 -> Pixel TF-322 hotshoe to sync cable adapter -> Flashpoint FPBF120 strobe.

The strobe only fires the first time I hit the shutter button; after that, the camera takes a shot, but the strobe doesn’t fire. The strobe has an LED indicator and emits an audible beep when it’s recharged, so not an issue of insufficient recharge time.

If I unplug the sync cable and short the contacts w/ a pair of tweezers, the strobe fires reliably every time. Power cycling the strobe allows it to again fire a single shot. The strobe also triggers reliably in slave mode, using the on-camera flash as the master.

Not sure if I should be looking at the camera, the adapter, or the strobe itself for the problem. Can’t find any menu options on the D5600 that seem to be relevant.

Will grab a multimeter and probe the contacts of the hot shoe to see what’s going on, but thought this might be an issue someone’s encountered before.