URL category allowed - blocked with noauth-protocol

Hi All - anyone throw any light on the below please?

Example User is called Fred, he is allowed to go to a gambling site. He could “get to” all of them – but the some sites eg 888casino and betfred don’t actually load – either a blank page or a landing page with a “there might be something wrong with the connection”,

The logs show non https traffic is allowed. But https traffic is not allowed and shows

Not using ZCC

We have advanced settings on to allow unauth traffic.