Yeah, I can't believe how stupidly locked down some of these networks are.
I once had an employer said they needed a "whitelist" of websites we wanted to visit instead of a "blacklist" of ones we shouldn't. That was an interesting day...
We run a Saas and someone wrote an email saying that our server was down, and when we'd expect it to be up. Not having had a notification, I double checked from a couple of geographic locations that our application was indeed up and responding.
After a bit of investigation, it turns out that they have to whitelist every unique address with their corporate IT. And had only whitelisted our primary client-app URL (talks to a couple of different API endpoints), hence the strange error message.
It's been a long time since I've worked somewhere with whitelisting.
I still maintain one on an internal QA network.
It allows whitelists.
https://avolio.com/fwtk-history/
https://www.ranum.com/security/computer_security/editorials/...
A tale as old as time: https://www.youtube.com/watch?v=uRGljemfwUE