A classical case of Dropbox website working on every device in network, except a single PC. But, sadly, even with all the support on other similar topics, I couldn't connect to the website.
I have tried using different browsers, turning proxy, antivirus and vpn on and off, using different DNS servers and removing the "hosts" file. So now, when I have tried every other option, I'm trying to reach for support of the community.
My best guess is that the issue persists due to some setting or error in router, but for some reason it works perfectly on any other device.