Strobe won't fire

We're using a P45 back with a Schnieder Kreuznack 120 on Mac V10.3.9 with Capture One 3.7.7. Today, out of the blue, tripping the shutter no longer fired the strobe. When I bypass the back and go directly to the pack it fires. We tried it on another computer and it didn't work there as well. A P 21 fired the strobe once but not again. The same for an H20 on a Hassie. The P21 and the H20 work fine on the second computer. Any ideas?

Turned out it was the cable from the back to the strobe. Curious though because when connected directly to the lens it fired. Must have been an ohm issue.