I am having the same issue.[br]
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I bought a new Cat 6 Ethernet cable. Cable internet is 300Mbit, but speed tests have me maxing out at 100Mbit -- that was the limitation for Cat-5, but Cat 6 should go up to 1Gbit with this computer. This lead me to troubleshooting the issue, and one glaring issue that may be causing this is that ***the new Cat 6 goes in, but does not click into my Macbook 2012 Pro 13" or my wife's. It does click on each end of the cable into my modem/router.***[br]
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I tried my old Cat 5 cable in every port and each end of it always clicks into every device, even the Macbooks.[br]
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I have deduced that ***there is something wrong with the shape of the new Cat 6 cable I have.*** Comparing the dimensions and contours side to side, and can not see any different in their shape or side that tells me why the Cat 6 won't plug in.[br]
It was only $5 for a 10 foot, so it ''is'' a cheap cable.
I read that if there are any wiring/crimping issues, the fewer viable wires would cause speed to go down to 100Mbit. So that may be an issue to look into as well.[br]
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Anyone else have issues with some Ethernet connectors not fitting into Macbooks? Are they all the same exact shape/form factor?[br]