Sometimes while on my office VPN, I am not able to access any of the Stack Exchange sites, while I am able to access everything else.
This happens once in a while, not everytime. When it happens, I try to open stackoverflow.com and the page does not load, instead times out after some time.
I tried to ask the IT group whether these group of sites was blocked, and it isn't so.
Sometimes reconnecting to VPN resolves the issue.
I am puzzled, and don't understand why this could happen.
Is there a series of diagnostics that I can try next time I see this behaviour to understand what is happening?