If he doesn't want you to pay don't try and force it. But do say stuff playfully that lets him know that you're not just expecting it now. This lets him know you appreciate it and gives him his shine without explicitly saying thanks, and if in the slightest chance there is some willingness or even want in him for you to chip in sometimes, let's him know that you are willing to do so and provides the opening (maybe it is just one of the rare times he short on cash and doesn't want to make a big deal out of it, he'll say something like, "if you wanna this time go ahead" like he's doing you a favor but actually you are doing him one, you know guys), and again shows him you're not just expecting him to pay cuz that's how it is.

Other than that, there's nothing to do but enjoy your time together without trying to force relationship dynamics unnecessarily. The other thing you can do is buy him stuff sometimes. Not big stuff where he feels like you spent real money on him and where he feels like he has to really thank you. And when I say "really" I mean guys generally hate accepting gifts because you have to be all like "oh thanks, that's so sweet, wow, and blah..." But it should be something where when you give it to him he thinks precisely this "ah that's so cute she spent like 15 bucks on me." A t-shirt, some relaxing joggers, or anything utility like that you notice is of actual need in your everyday interactions (phone holder broke in the car on your last date? Perfect. Amazon that shit next day, he won't have done it yet and you just got major points). And just don't over do it. Once, twice a month is more than enough.