So it IS about your own hurt then? Not about it being better for your daughter or grandchildren to be in contact with you than in a family group together with their father, but about the pain that you feel? about them not wanting you in their lives? If you get it clear in your own mind just what is the thing that is troubling you most, you can begin the healing process.
If you have a physical pain, you go to the GP to sort it out and find you the treatment that will ease it. There are people who can find you ways to ease the emotional pain too. When that has lessened, it will be easier to accept the loss. It won't take away the loss - as four years has not taken away the loss of my dear husband, but life goes on without him, and it seems to me that your life must go on, without your daughter and her family.
In comparing loss with loss, I have not said that I have lost more than you, Celebgran, I have said "as traumatic an experience as an estrangement" and believe me, his illness, and his death and his absence from my life were traumatic and still are. I had him for 52 years, he was the other half of me. I think the last few weeks of his life, when he was at home mostly under my care, will stay in my mind for ever.
BUT if the memories caused me as much grief and anguish as several posters still feel years after an estrangement, then I would go to my GP and ask to be referred for someone qualified to help me.