Not able to open a particular site from some networks ? Mostly when on mobile data is this happening to you ?

In some networks, it would be fine, but for some networks, you may end up not
loading anything and get the browser error.

Try to run a ping test to the site.

Check the result you are getting. Are you getting a response with an IPv6 in it ?

If so, that is screwing you up. When some providers function default on IPv6 and the
server is not equipped to handle it, this happens.

Easy fix is to remove the AAAA ( IPv6 ) DNS record from the NS and then refresh the browser.