Ethernet cord doesn’t work

[Korin]

When I plug my Ethernet cord to both router and modem the green light doesn’t blink and it doesn’t detect any cables in the app how can I fix it?

[FURRYe38]

Not much to go on. 
What Router and modem brand and model# do you have?

What CAT# lan cable are you using? CAT6 would be recommended.

Has a power off for 1 minute then back ON with the ISP modem and router been performed since last update?
Be sure to restart your network in this sequence:
Turn off and unplug modem.
Turn off router and computers.
Plug in and turn on modem. Wait 2 minutes for it to connect.
Turn on the router and wait 2 minutes for it to connect.
Turn on computers and rest of network.