What security/Anti-Virus software do you have installed? Try disabling it temporarily. Try a different Ethernet cable, try a different Ethernet port on the Router.
If you have a separate Router and Modem, try plugging the Ethernet directly into the modem temporarily and see if you can then access those sites.
If so, boot into Router setup and see if any sites are blocked or there are any rules in place.
If you have a separate Router and Modem, try plugging the Ethernet directly into the modem temporarily and see if you can then access those sites.
If so, boot into Router setup and see if any sites are blocked or there are any rules in place.