Simple suggestion but anyway.
Pay careful attention to her for hours before bed (if you don't do this already).
Treat her like a goddess, take a bath or shower with her, undress and wash her, you know...
Set the mood.
Furk. That works but to have to do all that crap every time you want a bit of nookie is hard work and a serious turn off. It almost becomes like begging for sex. There needs to be some kind of attraction to start.
My wife also struggled with low to zero libido for years. It was rough. We also checked for hormones and all that. She would always provide when I wanted it but the feeling that she was doing a duty rather than sharing an experience was a massive turn off for me.
Yea I'll say it again. It was rough.
It was like that for about 2 years, then over a period of about 6 months or so suddenly for no apparent reason she 'woke up' again. Things are back to the way they should be now. Have been for about 3 years or so.