My lo dont know how to suck from straw cup and just kept biting the straw. How can i encourage her or teach her? Im using the richell setq

My LO is 7 mth old. He can suck from adult straw the first time we presented to him at the end of 6mth but he has problem sucking from his Pigeon straw cup. Both hb n I tried n we find that it is so much more difficult to suck from his Pigeon straw cup which we don't understand y.need to use so much more energy . Maybe u can try to give ur LO different straws to try instead