Mike it may well be that he is simply unused to having hides provided for him. While instinct should by theory drive him to seek a hide, not all do. I have some that I literally have had to point their head into the doorway of their hide for them to get the idea. LOL Once they figure it out though they do seem to love their hides.

Do measure the temps if possible inside that warm side hide. Some hides depending on their construction retain/build heat to such a degree that it becomes overly warm and drives the snake from the hide so it's best to get the actualy inside the hide temp on a warm side hide.

Watch that overhead heat lamp. While it can provide the heat you need, it will also tend to suck the humidity out of that tank (if you've got the typical open mesh lid on it). It does look though that your humidity is good but it's just something to keep a close eye on so the snake can be healthy and shed well.