I keep mine in a stall without any other feed. So they are really hungry when it is time to eat. Then once they are good on the bottle, I start to leave hay and feed out for them.
If he's been on food other than milk, it might be harder now to switch him over. I would just keep trying to force it until he figures it out. It usually takes me about 3 days for them to get attatched to me and start looking for a bottle.
I have a 3 year old adult doe now that I got at about 5 weeks, and tried to put her on the bottle. At the time she was wild, and didn't want any part of it. I tried for weeks, but she refused and only wanted feed. She was one of my future show Boers, and since she was already eating plenty of extremely high quality grain and hay, I just stopped worrying with the bottle. She turned out great with no issues, and is the best producing doe I own. She was on very high quality feed though, and had been started on feed before I got her so she was used to it already.
Good luck with the baby! I like to keep them on milk as long as possible. But I guess there is always an exception? Maybe someone else will have some better tips.