My baby is managed to use straw cup now. Be patient, you need sometime to assist him. Let him practice more and he will know the technic one day, don't worry!
andrea manage to use the combi straw cup at 10 months. i bought the 4th stage one, may be let her try soon.
i agree also that u need to spend more time to let your baby try. my friend has no patient and now her son is already 17 months still hasn't start using the straw cup.
My daughter still can't manage the combi straw cup. Everytime i give her the cup, she just laugh and play the straw, so i use a spoon or milk bottle to feed her water or juice. I hope she can manage the cup later.
or u can try this way (the sales girl taught me)
u also use a straw to drink/ sip the drinks together with your bb. she might then know what is happening.