Content filter no longer working

Question

I adjusted Default Content Filter action to prevent Nudity sites from being accessible with success a couple years ago. However, I checked the other day, and even though my setting are still intact, I am able to access Nudity sites. If I use the policy test option, it says "blocked" as it should. But, again, I am able to open a browser and access Nudity sites. This feature was working perfectly last year. Not sure when it stopped. Suggestions?

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BAlfson · Accepted Answer

Agreed with Doug about having the Default Profile in Transparent and a Standard-mode Profile for the same subnet. 
 Configuring HTTP/S proxy access with AD SSO contains information about creating a GPO to distribute Proxy settings to everyone. 
 You might be interested in a document I maintain that I make available to members of the UTM Community, Patrick, "Configure HTTP Proxy for a Network of Guests." If you would like me to send you this document, PM me your email address. For German-speaking members, I also maintain a version auf Deutsch initially translated by fellow member hallowach when he and I did a major revision in 2013. 
 Cheers - Bob

DouglasFoster · Answer

Based on all that has been said, it appears that the automatic configuration mechanism stopped working, and as a result the proxy was bypassed. Most likely, the DNS (or DHCP) entry for WPAD got deleted by accident, or a machine that was configured with DHCP switched to static IP and no longer received the WPAD data because it no longer talked to the DHCP server. 
 If the UTM is inline to the internet, you need to enable Transparent Web to detect and intercept these situations. If it is not inline, I suggest you change to a bridge mode configuration, because it allowed me to move from out-of-band to in-band without changing any addressing. Then enable Transparent Web as backup to Standard Web 
 See my post here for details of my transition to in-band, and feel free to send a Private Message if you have follow-up questions. 
 https://community.sophos.com/products/unified-threat-management/f/web-protection-web-filtering-application-visibility-control/101117/optimizing-web-proxy-lessons-learned