"I am 50 and she is 59. We’ve been married for two years. At first, we had sex all the time. But in 2020, we didn’t have sex all year. She tells me I have to tell her when I want sex, but when I do, she always says we’ll do it tomorrow. Is there anything we can do?"
Clearly there’s a big problem in your relationship. I can’t tell from what you said whether your wife doesn’t want sex at all, doesn’t want it with you, wants a different kind of sex, finds sex uncomfortable, or any number of other possibilities. I asked you a few questions in email and got very little information, so I’m guessing that the two of you don’t communicate easily.
You can’t solve the problem until you know what it is. I strongly advise you to work with a good therapist or couples counselor to get the problem(s) out in the open, talk about what is preventing intimacy in your marriage, and figure out where to go from here. Therapists are working during the pandemic via phone and video call, so please don’t put this off—your marriage may depend on it.