Oh, Chrissiegirl, my heart aches for you! So painful to be CO (cut off) from your daughter and the GC as well! I am so sorry!
If the kids are little, though, I wouldn't take too seriously the comment that they "don't want to see you." Chances are, that's just their mum's viewpoint. I doubt they were even asked. If they're a little older, they still are, after all, under their mum's influence. They/you may not know how they really feel till they are adults or, at least, teenagers. Unfortunately, their mum said she "wanted nothing to do with" you, and, often, sadly, that means one doesn't get to see the GC either. Hugs!
It sounds as if, during those first few weeks of silence, your ED (estranged daughter) decided she would rather keep her distance. Or, if her husband is truly controlling, he may have used that time to convince her not to see you at all. Either way, I know it hurts.
I don't mean to worry you, but, IMO, it's a red flag that she also CO her sister. Controlling spouses often try to isolate the other spouse from as many of their side of the family as possible. Sadly, that could be what's happening.
However, do you know if her sis tried to convince her to reconcile w/ you? If she did, that may not have landed well and may be the reason sis was CO, too. Iv often read/heard that this can happen when one family member tries to intercede on behalf of another.
I can see sending your ED one more text or email, just to let her know you still love her and the GC and that the door is always open. After that, hard as it may be, I would back off. As agnurse says, ED may see continued contact as disrespecting her wishes. If so, that may decrease the chances that she'll have a change of heart.
I hope she does have a change of heart though - and sooner rather than later. For now, more hugs!