How do I make him cum?! (ORAL)

I’m 21 and I’ve only had 4 boyfriends (2 which were circumcised and 2 that weren’t). The two that were circumcised it was easy to make them cum giving them oral. They even physically show that they loved it(moans,eye rolls,etc...) with my new boyfriend (one of the two that aren’t circumcised) I cant get him to cum (same situation with my ex who was circumcised) with both of them I could never get them to cum giving them oral and they both just kinda sat there. Without pushing my head down guiding me in the right direction or anything. I don’t know. Any tips?