Ah, I see. It is hard and sometimes hurtful when that distancing happens. The best that your husband and you can do is just to keep that welcome open. My SD is awful at staying in touch, replying to messages, answering calls etc.
I know that teen shift when we stop being main characters in their lives as much as friends exists but it's harder when that teen isn't living in your home the whole time. We've had no falling out and her mum has never been one to poison her against us, we're all really lucky that way and get on well, but still I know my DH gets upset when it feels that she's opting out of his life.
We kept her bedroom for her long after she stopped sleeping here 3 nights a week, she was the one who suggested one of her brothers should have it so he gets his own space. We checked that she was absolutely sure and we've kept it as a room that still has her things in as well as his and if she sleeps over (very very rarely now) he'll camp on the sofa or on my youngest's bunks.
She's still invited to every meal out, visits to family, holidays, mini trips, weddings, concerts, gigs, events etc and she'll opt in or out depending on her work shifts and her busy social life.
So, rather a long winded way of saying it's hard but keep the welcome open, keep reaching out, you can't force them to feel it's home but you and your DH can make and maintain it as a home for them to always be welcome in.