To “cum” (orgasm) from prostate play alone requires regular practice and focus on the sensations that your prostate is giving you. In my experience, I had to work at it to take it from “interesting” to “oh woah that’s amazing”. And even the, I need to be in the right mindset to really enjoy it. Don’t give up! It’s something we get to enjoy that women don’t, as they don’t have a prostate :-)