Chrome will only block UserChecks for sites whose certificates are pinned in the browser, which will always include google-owned sites (youtube, google.com, etc) and key major sites like fakebook. Chrome is sensing what it perceives to be a man in the middle attack and blocking it, and there is no way to disable this that I know of.
The purpose of UserChecks is attempting to notify the user that their connection was blocked (it is not a connectivity/DNS problem), and provide a reference number they can use when trying to find the specific block event in the logs. However there are a variety of technical situations where a UserCheck cannot be sent to the user, or it is sent but the user cannot see it. You have run into one of those situations. Another example: any blocks/drops by the IPS blade will never send a UserCheck as IPS does not support that feature at all.
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