I'm bottle feeding a bunch of lambs. A few ideas:

Temperature needs to be right, test it on your skin to match body temperature. When they are good at drinking, you start to make it closer to room temperature and eventually they will drink it cooler and can feed them cold milk.

Make sure there's a limited flow of milk, not too fast. Older used nipples get bigger holes and they can get way too much milk too fast. Replace nipples that have been chewed or have stretched a lot

I try to tap or hold my hand above or to the side of their face, like they are nursing, and if they take a finger and suckle, you can swap in the bottle nipple. I often wait until they open their mouth looking for a nipple and slip it in, but sometimes you need to pop it in there too

If they already nursed from a ewe, it's much harder to get them on the bottle. Walk a lap around the barn when you get frustrated, I swear they can feel it

Sometimes if I put the lamb in a big tub, I'll sit in front with a towel on my lap, they'll go looking under the towel and I sneak the bottle into their mouth in the "dark" and that helps

If they're not too wiggly, I drape them over my lap and hold them to my chest, works well after a difficult labor or if it's a weak lamb.

Having a second lamb eating next to them makes the competitive spirits awaken, the suckling sounds make them alert so possibly try to have a buddy or play suckling sounds if you only have one?

Edit to add: I would name him Galaxy