I had a similar problem with my bunny and the bed. She was completely litter trained, but then we moved and she for some reason she kept peeing by the front door and on my bed.
I kept cleaning the floor with vinegar, but my bunny must be the only one that isn't deterred by the smell. So we eventually blocked all the areas she went to to pee, didn't let her on the bed and eventually she went back to her litter tray and hasn't peed anywhere else since.
I think it was a territory marking area, and once we stopped her going there and she got used to the place she stopped doing it.
I would just use vinegar around areas he/she pees, don't let them on the sofa, build up a cushion blockade when you have to leave the house. Eventually they will understand.
Is your bunny litter trained? If not, then this could help as they like to choose certain places to pee and keep going back to those places.
If your bunny can still smell his/her pee on the sofa they may have crowned this their bathroom. You would probably need to take covers or pillows to a dry cleaner to have the smell removed completely.
Hope this helps!