Celebi uncatchable.
Title says it all. I cannot catch celebi on my phone.
AR mode has never worked on my phone (it shows the AR picture but no Pokemon will appear on it) for some unfathomable reason the game says you must catch celebi in AR mode. If I try to catch it without AR on, I get this weird image of celebi that is uncatchable and keeps disappearing and reappearing.
Tried it on someone else's phone, same result. Except if I try using AR mode a blank black screen appears.
Any solution?

Answers
I imagine it's similar to the Mew quest where it takes 3 hits to catch.
You should still be able to catch it without AR mode. AR doesn't work on my fiancee's phone and the game was able to detect that during the Mew quest. It just swapped it back to the generic background shown in your photo and after a few balls it stayed caught.