Incorrect pinout refers to the wiring configuration of the cable not following the proper standard, which could result in connectivity issues such as no link lights and intermittent blinking on the NIC. These symptoms suggest there might be a problem with the cable's wiring, which was the last change made before the issue. A wrong transceiver would typically prevent connection entirely rather than causing intermittent issues and slow speeds. A switched VLAN would usually cause a lack of connectivity if the device was placed in the wrong VLAN. Finally, while dirty optical cables can cause signal loss, this would not apply to an Ethernet copper cable installation.