Granny from a distance

I am at a loss for words. I don’t know what to do. Without going into too much detail, I will try to explain why I need advice from you all. I am a mother of 2 grown sons. My youngest son, almost 24, has agreed to give up his rights to his son. I had been having visits with my only grandchild for some time now. My son and I have a very rocky relationship. This is due to his choice of his current wife over his son. He says it’s because of my controlling behavior. I do not like his wife, put it that way.
Anyway, my Grandson’s mother had informed me that she no longer wanted any contact with my son’s family other than me. No one else was to be told anything about my Grandson. I followed her wishes to the max. I never mentioned his name to anyone else in my family. Never. But, apparently on Father’s day, my son had contacted my grandson’s mother and they had a conversation about something that shouldn’t have been spoken about between them, in my opinion. I was informed of this conversation by the mother. I then messaged my son and asked him a simple question because what he had done hurt me so much. He messaged me back and then contacted the mother of his son. She then messaged me and told me that he was mad at her for telling me about what was said in the conversation between them, and that he would never tell her anything again. She then said “that is the reason I don’t have friends.” And she blocked me. I now have no contact with my Grandson AGAIN , and I don’t know what to do about it. All I did was ask a simple question. Now, what do I do? I want visits with my Grandson. My son gave up his rights, but I didn’t. Can I fight legally to have visits with my Grandson? Where do I stand and how do I start?