While attempting to set up an app that uses Auth0, we have uncovered a curious problem that Auth0 may need to report to AWS to resolve.
Whenever cdn.auth0.com resolves to an AWS 13.x.x.x IP, https://cdn.auth0.com… is accessible in China. However, when cdn.auth0.com resolves to the AWS 99.84.206.110 IP or another 99.84.206.x IP, then the cdn.auth0.com URL referenced does not work with HTTPS and the app login page does not load and does not work…from China (or parts of China). cdn.auth0.com is accessible via http, but no one wants that.
It appears that China is blocking traffic on port 443 on the AWS IPs that begin with 99.84.206.x (this is also affecting some other apps we use that are hosted on AWS when one of their host names resolves to a 99.84.206.x IP). Connecting to these URLs on the AWS 98.84.206.x IPs on port 443 outside of China works fine.
If you can get AWS to fix this in some way, it may very well resolve the China issues with Auth0…providing that you are also not using any Google elements, which are all blocked in China.