They sold you a bottle baby that was never raised on the bottle?


So sorry you are now responsible for trying to get a 2 week old kid trained. That was irresponsible of them!
So- to help you



What milk are you feeding?
Sudden change will be difficult because it tastes different.
Second, what nipple are you using?
A picture would be useful if you can post one.
You may need to try different nipples. You also want the milk to be very warm 100 degrees F.
Sometimes stroking down the nose will cause them to open up their mouth.
You may need to hover over them and almost shield their eyes, think like a momma goat.
Sometimes you need to put the nipple in and keep your hand around their mouth gently, do not squeeze the bottle or squirt it in.
Some put Karo syrup on the tip of the nipple... we never have.
If the kid is weak you will need to get some nutridrench and syringe a few ml's into his mouth.
If they are low on sugars they become lethargic and don't want to eat.
Make sure he is not cold! Put your finger in his mouth, if cold you must get temperature (body) up before you feed.