Grrr… let this be a lesson: don’t assume that the error message returned knows what the problem is. The message ERR_INTERNET_DISCONNECTED may well not mean what it says.
Connection reset? Generally, that indicates a TCP issue at some link in the chain — and there are a huge number of links in that chain. But, let’s have a quick look at things: Internet is fine. Connectivity is fine. Things are working fine.
Maybe the browser can’t resolve that site.
How would we check?
Just ask DNS — DNS resolution in my network is every device forwarding to a single DNS node, which then forwards first to 126.96.36.199 then to 188.8.131.52 if the first one isn’t available. It will not switch between them unless a DNS server is unreachable.
I begin with an assumption that my resolver is fine. I tried a few generally unused hosts to see if they could resolve.
john:~ john$ dig @184.108.40.206 one-confluence.pearson.com | grep -v "^;"
We also just have it throw out anything that begins with a semicolon, because at the moment, we don’t care. We only want to see the results. Hmm… nothing. Okay, let’s try the alternate resolver:
john:~ john$ dig @220.127.116.11 one-confluence.pearson.com | grep -v "^;"
one-confluence.pearson.com. 126 IN CNAME one-confluence.glb.pearson.com.
one-confluence.glb.pearson.com. 29 IN A 18.104.22.168
Ah! Well, that's different.
A quick tweak to the router, and a refresh of the IP info on the workstation and…
Summary: yes, the errors mean things, but sometimes a developer jumps to their own conclusions.
Also, this tends to underscore that the two resolvers are not identical, nor are they expected to be.