Domain and sub-domains are being blocked even though they are allowed in the proxy's policy
The top level domain (example.com) is allowed, but some of the lower domains (health.example.com, or safety.example.com) are being blocked. Why?
The web site is running Google analytics (google-analytics.com/ga.js), which is being blocked by the proxy
A policy trace will show that the blocked page was calling Google analytics and that was causing the site to be blocked. Once Google analytics was allowed in policy, the problem went away and the blocked domain was not longer blocked.