Well I just tried what you said and no luck. Let me explain as much as possible what is going on just to make sure I am not the one causing the problem.
First I have two computers networked together. 1 (desktop) is hard-lined (RJ45 cable from router to computer) into the cpu and the other is connected via the Wi-Fi of said router.
Second, I created a few encounters on roll20, gave link to my son and while he was on laptop, he connected. I had issues with the mic not working (also no cam at the time), but he saw what I was doing on the maps and I saw as he moved his token. The rolls worked well and we could both see what each was rolling or text-chatting.
Third, I deleted an encounter and added a new map and encounter to test the mic and webcam I purchased for the desktop. When I gave the same link that previously worked, he received the unauthorized page. I tried it again to make sure I did not mis-type the URL, but still received the Unauthorized webpage. I tried another encounter/campaign I was setting up still the same problem.
Fourth, I decided to create an encounter map from the laptop (son´s account) and generate a link. I tried to connect to his campaign with my account and I received the same result.
Fifth, I went to my web browser and cleared my history (it included cookies) and tried that, still unable to connect to each other. I tried the link from my own account and it open a web page with the campaign. I copied the link and emailed it to myself and tried from there and it worked while I was on my desktop. Went to my laptop with son signed in and he tried the link I e-mailed, and still no luck connecting. I do not know anyone else to try this with, so I do not know if this is only because I am trying to connect from the same router or because of my location (currently in the Republic of Panama).
I hope the information I provided was adequate enough to see if there is something I am doing wrong. If possible I would like to create a temp encounter map and connect with a volunteer, just to test my mic, webcam, and the capability to actually connect with someone else. I really enjoy the program, as I can put together my games with ease, but this inability to connect is really wearing on my nerves :-(
Regards