To clarify, because I have trouble-shot standard NL4 SpeakOn plugs not fitting when the cable was successfully used with one of our amps and cabinets, is that GK uses the NL2 jacks which are NOT compatible with industry standard NL4 plugs. The NL2 plug and jack are not new or newer.
In short, almost all manufacturers use NL4 jacks or combo jacks on amps and speakers which are compatible with both NL2 and NL4 plugs. GK uses NL2 jacks which are ONLY compatible with NL2 plugs and NOT with NL4 plugs. Do NOT try to force an NL4 plug into an NL2 jack, things will break on both sides.