Q: "This site can't be reached"

Hi,

I am currently having a problem opening certain pages on Chrome (although the issue is still present on safari, firefox, etc. Chrome is just my browser of choice). When I go to certain websites, such as twitter or reddit, I am prompted with this page:

Certain websites, like google, apple, and facebook, are working fine. I checked my extensions, nothing there except Adblock, google docs, google sheets, etc. I even cleared my DNS catche as recommended on other posts similar to mine. I've been trying things (to the best of my ability, I'm not a computer expert) for several hours and I can't seem to figure out the problem. It's very frustrating. For the record, I'm on a Macbook Air with MacOS Sierra version 10.12, although this was happening before I upgraded to Sierra.

Please help me!