Can’t load some websites? Check your DNS server settings

My older kid was trying to apply for college at a university in Florida. Perversely, its website refused to appear. He tried Safari, Firefox, and Chrome on his Mac and Safari on his iPhone. Only his devices appeared to be affected. Switching to cellular worked, isolating the problem to our local network. Yet my Mac laptop could reach the site just fine. Reviewing our routers and other settings, I couldn’t find a reason for this failure.What I finally discovered? Our primary network and Wi