Why can’t we get a diagnosis?

My 11 year old daughter has been feeling/not to mention looking sick since mid-July. After going to the pediatrician like 4 times in a month for symptoms like: persistent low grade fever, persistent nausea, occasional belly pain, fatigue, and joint pain; the pediatrician sent us to an endocrinologist whom ran about every lab under the sun. She threw in a celiac panel just to rule it out. Well, turns out her DGP IGG was positive at 34; so, we were sent to GI. GI doc obviously wasn’t convinced by just the DGP number (her TTG IGA was 11.3 lab reference range is <15.0), decided to do an endoscopy. Endoscopy came back positive, but damage was in the proximal jejunum, which seemed to perplex her doctor and he told me we were in a “grey zone”, and ordered genetic testing. Genetic testing came back positive for HLA DQ2… So, I’m thinking ok, we have a diagnosis… But, nope! He said we’re still in a “grey zone”, and wants to try a gluten free diet for three months to see how she responds.

What are your thoughts on this? I’m thinking this looks pretty positive for celiac, but I’m so confused as to why the doctor won’t diagnose it? Her doctor always seems rushed, and he’s not very easy to talk to; so, I’ve already made an appointment with another doctor (couldn’t get in till April). Just curious on what you all think!

Sorry for the long post and TIA!