Couple of Websites not loading anymore

[RLR]

We've come accross a couple of websites that use to work but are now not loading and return a ERR_CONNETION_TIMED_OUT message. I've checked various things on our network and also put my machine into a policy on the firewall to not be filtered but I'm still getting the issue. I don't believe it's device based as it happens on iPad and Windows machines. The websites work fine on 4G

 

The only other thing I can think it might be is they've got some sort of blocking enabled based on Public IP address or maybe too many users trying to access it at once.

 

Is anyone else able to see if they can access:

https://www.admissionstesting.org/

https://schoolsupporthub.cambridgeinternational.org/

 

Any ideas what might be causing this?

 

Edit:

 

Oddly adding "support." makes that part of the website work for us (https://support.admissionstesting.org)

 

I'm now pretty sure this has something to do with our ISP as both these websites that don't work resolve to an IP address owned by our ISP whereas the working website (https://support.admissionstesting.org) has a different IP not owned by our ISP.

Edited October 25, 2022 by RLR