It could be because of a medication you are on. Most antidepressants make it all but impossible to have an orgasm.
It's typical for sex drive to decrease after menopause. It shouldn't affect your ability to have an orgasm, but it's normal to notice a decreased interest. If your mind's not there, you aren't necessarily going to reach that "finish line," so to speak.
I went through the change at 43 and I have to adnit it changed my sex life considerably. I have never discussed it with my doctor but now that I know her better I guess that is as good a place as any to start! When you go through menopause your estrogen levels drop and so can interest! Not that sex was ever THAT important to me,, but now I could care less. I'm sure we are not the only women that have felt this way. I suggest you reach out to your doctor as well. I wish you the very best ... take care!