Ok so it sounds like you have tried most things. Although I would still have hay available to him, I would definately go with what Tamsin says, minimise the pellets, up the veggies and try and go for the highest fibre veggies you can find.
I'll always have hay available for him, I never give up hoping but I did give up trying every kind of hay there is. My other bunny did start eating hay when I tried a few different things (minimised his pellets and tried different kinds of hay) and now Indy just gets what Fred likes. Before that I bought every different or new kind of hay there was available to try if that helped..
As far as I know these are:
Herbs and other uncultivated leafs like weeds (check they can be eaten first) soft fruit leaves like strawberry, non stone fruit leaves like apples and some normal trees (not oak or conifers)
Kale/sprouts
Mangetout/sugar snap peas
cauliflower
corgette
celery
raspberry, blackberry, apple, pear, dried apricots (although limit because of sugar content)
Green beans - although remove the seeds as these are toxic.
Now there is quite a language barier I'm afraid, I have no idea what's meant by most words, but I'll see if I can translate it online, maybe that helps.
About the strawberryleaves: I feed him dried strawberryleaves now and he really loves them. Never really knew you can give fresh leaves as well. Now I'll try to translate everything first because me not getting half of it is not very helping of course
The one thing I would also ask, he stopped using the litter tray around the same time that he stopped eating hay? Given his age has the vet considered the possibility that he might be suffering from arthritis? if he was in pain then that could leave him to stop eating hay, even whilst continuing to eat everything else. If he is looking a bit stiff and like he might be in pain then a pain medication called metacam may help.
Well, the thing is, he didn't stop eating hay, he just never did. I think he just doesn't see it as food..
On the pain front, a molar spur, even if very small could still do the same thing. You can see in my siggi a netherland dwarf called Rosie. She has only had to have one dental in her life due to a molar spur. The only symptom that she displayed at first was not really eating as much hay as normal, I thought that this was possibly due to her being a bit on the tubby side and cut down her pellets which helped a bit but then a week later she started to dribble from the side of her mouth. Her spur was so tiny the vet could only just see it & didn't think it was big enough to cause the dribbling to the extent that she was but one dental later she was back to her normal self.
He just didn't change any eating habbit, the not eating hay has been this way for six years now. There wasn't even really a spur, just one tooth that's a tiny bit eh.. 'wrong'. But I'll ask my vet again. (Haven't spoken to him yet. Thursday my other rabbit will be neutered, I'm planning on leaving all the information such as the email from Oxbow etc for him then.)
We do get many rabbits in the rescue that do not eat hay when they first come in but I can't think of one off hand that we could not get eating hay again by the time we left, perhaps not masses for some dental buns but at least having a bit of a nibble.
