Why can't I feel pleasant sensation?

I've been attempting to follow Leigh Brasington's instructions about entering jhana. However, I never seem to be able to find a pleasant sensation. I mean I feel just kind of warm and comfortable in places and I feel occasional subtle vibration or tingle but not enough to maintain focus on. Anyone have any advice about this? And before you start to preach about how trying to enter jhanas will ensure you don't, I already know that. I'm just more looking for advise about why I can't seem to notice sensations much. Thanks