Mimzy is 9 years old this year and he's been willingly eating the Oxbow Support tablets (all six types of them) for a few years now. I don't know why a bunny wouldn't find them appealing, unless it's just too strong an aroma for them. How long have you been attempting to get them to eat them?
I know Mimzy won't touch certain herbs, like sage for example, as he just doesn't like the smell. Could you perhaps disguise the tablets inside something else they do like? Some mint, or other treat, that will help to mask the aroma of the tablets?
I will note that, although Mimzy seems happy with these, I often can't give him many of them due to him getting a messy bum afterwards, or not eating his cecotrophes. Also I am not entirely convinced they really help his joints. He eats the digestive, immune, urinary, senior, skin and coat and joint tablets and still has tummy trouble, achy joints, poor coat and bladder sludge problems, so I think these are a bit of a gimmick.
But he has to have something with his twice a day metacam to keep his stomach from getting the blast of painkiller, so....
There is also a product out there called myristol. It is used for horses who have joint problems. You might consider trying this instead. You can find a rabbit friendly product containing it here:
http://store.bunspace.com/Myristol-Pellets_p_59.html