Are you doing a regular bonding process each day, where you have them together in a neutral space, for an increasing length of time as the bonding process continues over the days/weeks? Running loose in a larger area isn't the same thing if they don't stay near each other so they can get to know one another, sort out their hierarchy, and form a bond. If they don't stay near one another, then a smaller space is needed, like a 3x3 pen, bathtub, or bathroom, etc. Otherwise they just avoid one another and no bond is able to form very well.
https://rabbitsindoors.weebly.com/bonding-bunnies.html
http://cottontails-rescue.org.uk/information/bonding-bunnies/
https://wabbitwiki.com/wiki/Bonding_rabbits_together
A larger room can sometimes work, as long as they aren't acting overly aggressive and trying to fight. But half hour isn't long enough each day, and it can take a lot longer for the bond to form, if it is able to form at all. But if you want to do it in a larger room, I would be gradually increasing the time to several hours a day, carefully supervised.
Another thing that might also be helpful is keeping them in side by side pens all the time until their bond is formed and you can keep them together permanently, if this is something that's possible for you to do. This way they can always see each other and get used to each others presence a lot better.
Nudging isn't necessarily behavior that you're needing to stop from happening. The rabbits have to have interactions where they can sort out hierarchy, or they'll never be able to form a bond. Though you do need to be watchful to make sure it doesn't escalate into too much aggression or a fight could break out. Minor chasing and nipping can be normal. Excessive chasing, excessive nipping, circling, does need to be stopped. If there are ears pinned back, tail raised, increased circling, jumping over the other rabbit, or actual biting happening(eg. latching on or trying to go for the belly), immediate intervention is needed, and bonding may not be able to proceed, depending on how bad the aggression is and each rabbits reaction.