VA won't refer us to Mayo, even if we requested

I have been fighting for my husband, 100% disabled veteran, to be seen at Mayo for unknown GI issues. I've called Mayo and know they accept VA Community Care, but I keep getting told by the VA that Mayo doesn't take it. They currently have him being seen at Shands hospital, but I need a team to look at the whole parts instead of hyper focusing on one. Everybody seems to keep missing the issue and he has been dealing with this for almost 3 years. It doesn't make sense to us that his bloodwork shows he's fighting an infection, yet they can't figure out what. Also, bloodwork will show that liver and kidneys are going bad at times then other times they are fine. His Shands doctor told him that he doesn't have Pancreatitis, however we've had multiple GI doctors confirm that he does including a different Shands doctor (who performed his scopes). Gallbladder has been removed and that didn't fix anything. Now we are back to him barely eating. He can't eat red meat or anything red (strawberries, watermelon, tomatoes, Fruit Punch, etc). For about a year all he could stomach was soup. I just want answers. Our kids want their dad back. Anybody have any tips that I can try to get him into Mayo Florida?