There may be underlying health issues related to his dysfunction, but another angle may be one that my late husband brought to light before he passed away a year and half ago. He was writing a book on sexual desire and relationships.
I read what he wrote and at first was hurt by what he had to say but took it to heart and did something about it....too late, I'm afraid...
He said in his book that as women age, they start to look more and more like men many of them wearing large t-shirts over jeans and tennis shoes, no make-up, short or dowdy hair, their shape takes on a round soft appearance and according to him love isn't enough to generate sexual desire.
Granted not everyone stays young looking and desirable as they age, but it is possible to turn a guy off by looking just like him.
I had gained about 40 lbs. and wore "proper" clothing, Cabin Creek gathered pants outfits and well, just anything that would cover my burgeoning body.
He just wasn't turned on by that and our sex life was very difficult.
I'm not saying this is your problem because you may be a total fox, but it did make a big difference in our marriage. My present husband doesn't even need V even though he is 59 and I am 56. We are like two teenagers even though much of the rest of our relationship sucks...at least that part is great.