Circling & chasing
Be sure they are in a SMALL, neutral area such as a bathroom or penned area. Stop the chasing. Place them side by side. Try feeding them treats together. Try car rides in a box together. Sometimes loud noises or being sprayed with a water bottle are enough to make the chasing stop. A little dab of peanut butter on each others head may instigate grooming.
True aggressive fighting
Separate buns and try again later. Try taking them for a car ride together in a box and back to a neutral place. Supervise closely. Check for wounds. Try another rabbit if this aggressive fighting persists. Call an HRS volunteer.
Ignoring each other
As long as they are not fighting, this is a good thing! If they are coexisting in their neutral space, this is typical and a good start. They will begin to sit closer, sleep near each other and eat together shortly. Leave them in a small neutral space a bit longer. Try to wait for a little grooming.
This is GREAT! Their relationship will probably continue to blossom from this point. Leave them in a neutral place for a few more days to continue the bonding, then SLOWLY introduce them to freedom in the house together. DO NOT SEPARATE THEM ONCE THEY ARE BONDED.