429 Too Many Requests

I can't access some websites like swisscows.com through this browser. This problem is only with Firefox (including nightly). Other browsers doesn't have this problem (Chrome & Opera). When I access these websites with Firefox, the websites shows "429 Too Many Requests". Iam not using any VPN/Tor/Proxy. (Only some sites have this issue, as i mentioned earlier & iam talking about Firefox for Android). No extensions are enabled. I deleted & reinstalled Firefox; but no use. I use swisscows as my search engine. Please fix this ASAP.