Ensure you are up to latest webCoRE on your system - if a user install HPM repair.
After installing, wait 10 mins, then politely reboot your hub.
The external URLs will change during the upgrade to a new hub, so you can check if they work by looking at the piston for the URL. The references may need to be changed in calling applications because the hub uid changes.
I was composing a long reply asking how to repair the built-in version of WebCore, etc; when I realized that my External URLs have just started working again.
Not exactly sure why. I regenerated the token for WebCore and randomly poked a bunch of other things. Suspecting either a caching issue or alien interference. Assigning roughly equal probability to each!
I think you're a bit low on the alien inteference side. Lots of jealousy from the outer ring planets since earth got the C-8 first. Glad you're up and running.