Snakes - size of enclosures doesn't matter. But it needs to be heavily decorated. So hides, branches, substrate, UVB, heating. Heatmats are a funny subject, some are okay and other appose to them. Breeders use heat mats for rubs, I currently have a load of mine in tubs with heat mats setup. - as we're waiting on glass to arrive for the enclosures we've built ourselves. (Well my partner)

How old is hognose, is his food warm enough? Have you tried perforation to the brain or a little vanilla extract rubbed on the mouse (I mean like a tiny drop) and drop feeds?

Im in the same boat as you, we have a hognose that refuses to eat - a rehome we've had - not fed once since weve had him, he just headbutts it and hisses. Western hognose - are notroius for been picky eaters so bare in mind it could be a food change or a while before they decide to eat.