Hi,
One question I haven't seen asked is how you prepare the snake and the meal before hand.
With mine I found that letting them defrost near the enclosure lets the snake know a meal is on the way. The eating sideways raises the thought that maybe you need to heat the head of the prey more ( that is generally how they key in on the head of the prey animal) with mine, once it is defrosted, I heat the head region with a hairdrier.
This has a dual purpose - it wafts the scent of the prey around a lot more just before offering, and it gives them a clear hotspot on the animal to aim for when presented.
Hope this helps.
*ETA* yes I would try the small mouse.
del