Unable to open Gmail via any browser on Macbook Pro

Hello everyone. I have a Macbook Pro macOS Mojave 10.14.6 and it's been a few days that I am unable to access Google Mail via any browser. Specifically, here is what happens:

I can access other Google Suites pages (Drive, Calendar) with no trouble.

When I go to mail.google.com I get the following error messages:

• In Safari: "Safari can't open this page."
• In Chrome: "This site can't be reached, server took too long to respond (err connection times out)."
• In Firefox: "Did not connect: potential security issues"

I tried to install Gmail app instead of accessing it trough a browser, and it didn't work as well.

I don't have this issue on any other Apple device or on my PC.

I tried all the basics: clear cache, history, disable plug ins, open in a private tab... And... nothing.

If it were just one browser, I would think it's a corrupted cookie file or something. But I don't see how that could affect multiple browsers.

Any thoughts? Thank you.