a certain website doesn't respond in Opera and Chrome

I can’t access one particular website (namely dictionary.cambridge.org) on my laptop. It was working fine yesterday but Chrome stopped displaying it in the evening. I thought website’s servers were down so didn’t pay much attention to it. Had tried to access it this morning but still have no luck.

Error description on both browsers I use is identical: site didn’t send any data. (Chrome error message: This page isn’t working dictionary.cambridge.org didn’t send any data.
ERR_EMPTY_RESPONSE)

Other details and what I’ve tried already:

• Can’t open it on neither Chrome nor Opera browser, but it does work on Firefox;
• Cleared cache on Chrome;
• Tried to open it using Opera’s built-in VPN;
• I can access cambridge.org and bookshelf.cambridge.org;
• The problems doesn’t seem to be related to my network – I can open the website on my phone and on my second laptop that are connected to the same WiFi network;
• I’ve restarted the system twice. Also I shutted the laptop down and turned it on again. It all didn’t help;
• I tried restarting network manager in a console;
• I have tried reconnecting to WiFi;
• I have tried to connect it to another WiFi using my mobile phone as a hotspot;
• I pinged dictionary.cambridge.org, the result was 100% packet loss (mtr –report dictionary.cambridge.org shows the same thing);
• I noticed that Chrome and Opera’s address line specifies that the website doesn’t use https ("Your connection to this site is not secure") but it does in Firefox;
• I don’t use any ad blockers (except Opera Ad Block which is built-in).

My os is Ubuntu 18.04.4 LTS.

I would be grateful for any help.