I'm having the same issue as well with Inserting videos from the content library.
In my case I can insert images from the content library no problem.
Previewing the video works but when I click Insert button it gives me the same error.
I'm a student using my Windows 11 laptop and no custom firewall settings or hosts file mappings.
Storyline 360 is up to date.
I can get to the images in the content library no problem and I'm assuming that's connecting over port 443 so I don't see the point in opening a bunch of firewall rules customized for services working connecting to articulate and many of the other sites mentioned in your article like unsplash.it i have no problem connecting to these other sites.
I didn't see anything from Storyline 360 in Event Viewer.
Do I have to try uninstalling and reinstalling to fix this? Any other suggestions? Thanks