Hi there,
can you give a bit more info about how long you’ve been doing sessions and how long you’ve pre-bonded?
It’s very normal (and a good sign actually) for the rabbits to ignore each other at first when they are in a new location.
I personally haven’t had good luck with small spaces, unless it’s during stressing (like a car ride). I have had much better luck with large spaces. That way if one rabbit is scared they can move away from the other rabbit, rather than feel forced to bite.
When in the area with them, try not to sit down in the area with them or pet them if they come up to you for comfort. You can, however, pet them and swap scents when they approach each other to help them start to trust each other.
It’s best not to force them to interact (aside from putting them in the bonding area together), as they are just learning to trust each other. “ignoring” can mean that they are scoping the other rabbit out and deciding whether they are a threat. So, any session where they are not aggressive is a positive one, especially early on in the process. With shy bunnies especially, they can need extra time and space to decide whether they trust the other bunny, so it’s important to go at the bunnies’ pace. 
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The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.