Why does the user get a CONNECTION_REFUSED error?

Question

linux

Strange error at one site user.
Can't login via mobile network on smartphone, CONNECTION_REFUSED error occurs. At the same time, all other sites work, and if you change the network and go, for example, via WiFi, then there are no problems.
What is mb connected with?

Answer 1

Obviously, the firewall or the web server itself is refusing.
Show the rules, the command depends on what you have there for fw.