I’ve experienced this. It’s very hard. In my case my child resumed contact when they were ready.
I struggled with my own mother and am estranged from family by my own choice so I have experienced it from both sides. What stopped me from reconciling with them was their belief that they are entitled to a relationship with me, and my belief (right or wrong) that they needed me and my children around to fulfil their needs at our expense.
Having been through it, I found it very difficult to be rejected by my own adult child. I tried to reassure them that I loved them, that I respected and supported their choices, and that I didn’t want anything from them that they were unable to give. I made it clear that my door was always open.
We went through counselling together which was very difficult and didn’t have any immediate success, though I think in the long term it probably did help us to understand just how poorly we were communicating, despite a real desire to sort things out from both sides.
I have often felt that I must be a terrible parent but that’s not necessarily true. Children turn away from their parents for lots of reasons, and very likely don’t grasp how painful that can be for the parent. Reconnecting requires reflection on both sides and lots of patience and faith.
I wish you well.