What can block access to the site (https://clients.open.ru/users/login)?

Question

Computer networks

A relative asked to find out if THIS site specifically does not work for him from any browser.
Checked hosts - nothing is forbidden there. Antivirus - no restrictions, firewall - no, turned it off. Nothing in the router.
When you go through the anonymizer - everything works.
They called Rostelecom (or Sibtelecom, something like that) in support, they say that the problem is in the computer, everything works for them.
Another site with https checked, works fine.
I think, maybe some "well-wisher", who has access to the computer, blocked access to him? But how can this be done, where else to look, help pliz?
ps The computer has not yet checked for viruses, I will check tomorrow.

Answer 1

Does www.open.ru open? What does tracert say? And how exactly does it not work? "Server not found"? Or what?

Answer 2

Perhaps the point is that the DNS has not yet been updated, although Rostelecom says that everything is chocolate and should work.
I installed Tor for a relative, for some reason everything worked through him.
If after a couple of days it starts working again on regular browsers, then there was a jamb of Rostelecom.
This link describes the same issue.