It took DS almost a month after we offered to get the hang of the sippy cup. We tried a few different kinds, you might have to do this. He was like your LO and would just "chew" on it. Eventually we got one that had a silicone tip (like the nipple for a bottle) and he understood that better. Also, we had to put more than a little liquid in his cup or else it wasn't getting to the tip and into his mouth because he didn't know to tip it up. He does now, but at first, we had to put lots of water in it. GOod luck, he will get the hang of it. I kept thinking "will he ever learn to use this?" and then one day he just did.