are you behind proxy ? if yes, does it require authentication ?
The Answer to your question is No, we are not behind proxy.
But we were able to find the around the issue looks like they broke something with 9.0.4 when you have Secure: Single Subdomain enabled on Add-ons >domain Security, So we switched that off and chose (Default) instead.
HTML tile and our other custom tile seem to be working fine now.