If you're seeing issues with inconsistent block page issues with Chrome for Mobile, please have your end user disable Chrome's Reduce Data usage feature. As an example, you may see certain pages being blocked in Chrome for Mobile when they are not blocked on another browser on the same mobile device or allowed when unexpected.
When this feature is enabled, all HTTP traffic from Chrome for Mobile gets redirected to a Google proxy at this address: compress.googlezip.net. The proxy then compresses the data and sends it back to the client. Unfortunately, when this happens, the proxy will perform it's own DNS requests against it's own DNS servers, which causes inconsistent block page issues as the DNS services are no longer with OpenDNS.
What to do
To resolve this, please have your end user disable Chrome's Reduce Data usage feature.
In Chrome for the iPhone, it is found under Chrome Settings > Bandwidth > Reduce Data Usage > Set to Off.
In Chrome for the Android, it is found under Chrome Settings > Reduce Data Usage > Set to Off.
For more information regarding how OpenDNS and proxies behave, please review this document here: https://support.opendns.com/entries/49509190-Using-OpenDNS-or-Umbrella-Insights-with-a-HTTP-Proxy
For information regarding the Google Reduce Data Usage proxy, please review this Google document here: https://support.google.com/chrome/answer/3517349?hl=en
If it's not possible to disable Chrome's Reduce Data Usage feature, please add compress.googlezip.net to your allow list in the Umbrella dashboard policy applicable to mobile devices. This ensures all DNS requests will be made via the proxy server and as such will not be directed to us. Unfortunately, this approaches means that your block pages belonging to OpenDNS will not work at all.
To block your users from using this functionality, add compress.googlezip.net to a block list or ensure that the category Proxies/Anonymizers is blocked.