Cream Puff - What Am I dong wrong?

Well, lets start with the recipe you are using, and go from there.

If you would post the recipe that would be very helpful.

 

What's your dough like? Oven temp? I've been told a higher temp start in the oven helps puff, undercooking makes them collapse also

 

If you mean that they deflated, it could be too wet dough or under baking. I used the link below and they came out perfectly, first time! Note the troubleshooting on the page. https://www.theflavorbender.com/how-to-make-perfect-choux-pastry/