My unterminated RJ45 8P8C connector won't fit into the port. Why?Updated 2 months ago

Regardless of what you are plugging your RJ45 8P8C connector into, it will need to be terminated first before it can fit into a port. 

RJ45 8P8C connectors have eight golden contact prongs. When coming from the factory, 8P8C connectors are not terminated and the golden contact prongs are in a "raised" position. During the termination process, the prongs are seated downward into the insulated conductor wires with a crimp tool. The prongs “bite” into the individual conductors when you terminate the cable. 

If the termination process has not occurred yet, the raised prongs will prevent you from plugging in the RJ45 8P8C connector. If you wish to "dry fit" a connector by sacrificing one you must place the connector into a termination tool and terminate the golden contact pins first, but without using a cable. It will now snap into the port, but be advised this process cannot be reversed so the plug in question will need to be discarded.