We resolved this issue at my job. I researched FW to the point of reading engineers’ blueprints & white papers on FW standards, & no one describes this:
Most FW cables out there don’t seem to work with Macs.
There are some FW cables that have little tiny holes in the ends, where the wires can be seen (otherwise you just see the wires on the sides of the central part in the interior of the plug. Those are the only cables we can get to reliably work with our 50 PowerMacs used for video editing. You can’t specify those cables, & no one addresses this difference. You have to look at a good image when you order or examine the cable ends.