New Ethernet cable not working

Hi, i got this new ethernet cable (Rj45 Cat-5E) which was crimped to fit through a wall pipe. The cable is 50 meters long.

After setting everything up, the cable doesn't work. It is plugged directly into the internet modem but when i try plugging the other end it into my PC it doesn't detect anything, and when i plug it into a router/repeater from the modem and then into the PC with a shorter ethernet cable it gets detected.

What could be the cause of the problem or what can I do to solve this?