I'm getting a nginx "403 forbidden" error across all my desktop browsers, including after clearing cache/cookies, and even using a different device entirely.
Oddly enough, I can use the site just fine with my mobile devices, and it works perfectly on my desktop if I switch my user agent to an older browser.
Chrome 71 shows "403 forbidden", but a spoofed useragent of Chrome 69 works fine. IE 11 (real or spoofed) shows the same error, but a useragent of IE 10 works fine. Firefox 64 shows the error, but a useragent of Firefox 63 works fine. And every mobile browser user agent works perfectly fine, regardless of being legitimately run on a mobile device or spoofed on a desktop browser.
I had the same results on a freshly formatted laptop, connected to my phone's wifi hotspot, so I'm certain it's not a software or ISP issue.