@Peoplecraft
Since you CAN connect via WiFi to the Internet, then probably the modem to router Internet connection is OK. So, now the question is what is wrong between the router and the OS.
If on WINDOWS, enter in a CMD prompt (Windows key + R key at the same time) IPCONFIG /ALL
You should see something like this in it with some number results different:
=================
IPv4 Address. . . . . . . . . . . : 192.168.0.166(Preferred)
Subnet Mask . . . . . . . . . . . : 255.255.255.0
Lease Obtained. . . . . . . . . . : Tuesday, December 15, 2020 6:34:44 AM
Lease Expires . . . . . . . . . . : Thursday, December 17, 2020 6:34:43 AM
Default Gateway . . . . . . . . . :192.168.0.1
DHCP Server . . . . . . . . . . . : 192.168.0.1
=================
One other question, is this wired NOT working on the SAME PC that it worked wireless on? Just curious.
When you say " I cannot connect to the router through ethernet but can through wifi " you later state it to the Internet. So, what were you using? A browser? Have you tried a different one? Also, if you were using a program, does another work? Lastly, what SPECIFIC error you getting? All these answers would help here.