Two troubleshooting methods:
1. Make sure Network Interface Card is seated properly.
2. If answer to 1 is yes, replace NIC.
This is assuming that you have router on network as DCHP server. It sounds like you’re getting IP and accessing the internet.
If you were not accessing the network, it would sound like firewall issues. This can especially be true if running software firewall on workstation and other IP’s on LAN are not listed as Trusted.
However, the wiggling of the wire points to a hardware issue. Being that you have replaced the Cat 5 cable, the next step is to investigate the NIC.