Possibly a case of low testosterone? I agree with Minnesota-nice. All those could be the reasons...how old is your husband? Men‘s testosterone level starts to drop in 30s, by the time they reach 50s or 60s, about 2 in 10 men suffer from ED especially if they have underlying health issues such as cardiovascular condition sleep apnea etc, even stress can trigger it ...some men aren’t even aware of it other than a drop in libido...

I was in the same shoes 8 mos ago. My husband is in 50s and I‘m still in 40s, throughout our marriage he was always the “Horny“ one but since the end of last year he had not shown interest in sex for a very long time, I ended up “service“ myself often...being women in 40s, we are at the peak of our libido. It was so lonely. I didn’t feel rejected but I felt super frustrated and discontent, at times even angry... I was‘t even looking for hot sex, just any sex...I totally understand how you feel.
The key is communication-I ended up talking to my husband. I asked him when was the last time he experienced an erection? When was the last time he masturbated? I told him I had been masturbating since he wasn’t interested in sex lately. Told him I have concerns about ED and even did researches on it. I even advised him to get T level checked. I was too desperate to worry about hurting his ego. If it’s a physical or health related issue, i will accept it, be supportive and understanding but I need to know. With Covid going on he couldn’t have a physical just to check T level. But just our talks helped. We had mismatched libido for years when he thought I was uninterested when his L was high-the reality was that our love-making routine had become unexciting to me, he wasn’t even aware that i had become sexually frustrated.

We ended sharing about what turns each other on-which is a bit different from when we were young. Just the fact he knew that I wanted to have sex with him helped -we had it right that night after I cried in his arms. We have sex quite often now ever since our conversation-from not once for 6 months to doing it 3 times a week. The psychological factors knowing that his wife really wants/desires him brought back his L. Granted, we are middle aged so I have much more realistic view of our sex life. Just like I’m going through premenopausal and my hormonal is raging up and down, my husband is approaching golden years and there are times he will not be in the mood. I also noticed some physical changes-e.g. He is quicker to climax than before (funny I always thought young men come quickly but older men take longer-guess not necessarily)-which is fine, with right kind of stimulation I still come. He’s alway prioritized my orgasm over his, i just wanted us to be intimate again and not to worry about performance for awhile.

My take is that when men approach certain age, even if they don’t suffer from ED, their libido will more or less be like women’s-less predictable. Some days they might be as horny as hell, some days they will not feel like it or maybe can’t even get it up-which is all part of normal life cycles. As long as you love each other and keep on communicating, and don’t take rejection personally. He‘s not rejecting you, he’s rejecting sex-maybe not even that, maybe he wants to be horny, but can’t...could be physical, could he stress or anything (Just like when women don’t want to have sex, there’s no one single answer to all cases)...you won’t know the underlying reasons unless you talk heart to heart...