@Ser 

Unplug port 1, will the router still have internet? If yes, that means line 2 is good, and port 2 is also good.

If no, you can plug line 2 to port 1 and check if it works. If still not working, line 2 may be broken. If it works on port 1, but not port 2, you need to check if you configure port 2 properly.

BTW,  how did you check it only gets internet from port 1 only?