At a place where I used to work, one of my duties was to see that client testing software worked with the local systems. Most of the time this was no big deal. But this one day the client software (which always word before) did not connect to the host's server. Student could not take their exams. Everyone seemed perplexed as allegedly everything was set up right. One tool you can test a connection is traceroute.
Not only can you test the connection, but you can find some interesting information about the connection. Having done that, became disappointed when we could not get the traceroute to work, Then I thought it could be an internet problem. There are sites that will let you run traceroute externally from your your network. Used the internet to find such a site. There are many.
Well guess what the internet administrator, gave us the wrong ipaddress to use. After that was resolved all was well again when the correct information was entered into the systems..