Puppy keeps holding it and does not go outside no matter what

Hello everyone, I have a cocker puppy which is around 16 weeks. The puppy never goes outside no matter what. I have him on a schedule, I always know when he needs to pee or poop. However, once we go outside, he holds it and never go. I tried waiting it out and we ended up staying outside for 3 hours, but still nothing. Did anyone face this? What can I do? It is getting super frustrating as I get super tired for literally nothing. The puppy is crate trained, so I tried shorter periods and put him in the crate and so on until he goes outside. He stills holds it so much until he pees sometimes in the crate. He never goes potty in crate and one time he did hold it for around 20 hours until he did it outside (only one time)

Thank you!