After struggling with this for quite a time, confused about how I could not access TC from my own dorm room, but only from the college library, I tried a myriad of solutions.

Using a different browser didn't work.
Putting the sites in the allow list didn't work.
Turning off Windows Firewall didn't work.
Clearing the cache and all history didn't work.
Switching internet connections didn't work.
Disabling the router's firewall didn't work.

However, someone pointed out that people with the AVG firewall can get the error, and I thought "But I don't have AVG."

But I DO have Avast, and after turning off their Web Shield provider, the site works fine.

This is interesting because I can go to Chat and load the chats there fine, I guess TC just pisses off Avast.

Put the web sheild sensitivity down to normal in avast and you will log in with out no problems