Specific sites not loading with R7450

Is there anything special about these websites that would require extra security measures?

Does this happen if you use a different browser? How about different devices?

I ask because routers rarely have much to do with how the web works unless you have enabled something like parental controls or Armor.

Browsers, on the other hand, are getting increasingly picky about what they deem to be dodgy sites. Even operating systems can cause headaches.

Do the router's logs show any hints?

Then the usual boilerplate questions to eliminate some of the more common issues.

What firmware version do you have on the device?

A number is more useful than "the latest". There may be newer versions, or "hot fixes", that do not show up if you check for new firmware in the browser interface.

If there is one it might also help if you told people the make and model number of the modem/gateway/ONT that sits between this router and the Internet. Is it, by any chance, also a router, with a set of LAN ports on the back?

I ask because a lot of people turn up here trying to put a router behind a modem that is also a router. That can complicate troubleshooting.