I was told not to have any visits, just pay the medical bills and leave. 40 years later I found her married with 3 children. She will email me, and ask many questions, ie; why didn't you... I told her the courts ordered me to keep away... Her mother we think wasn't to sure If was the real father of her child. The blood tests only show I was not excluded. This was in 1970. She had a meeting all set up with me and was going to call me the next day. Well she didn't. I asked 3 times by email over the past month if she was OK. No answer, but she is OK because she is on Facebook telling all the wonderful times she is having with friends, gatherings at her home and sending photos of her family. What can I do? I feel maybe she is worried about telling all her friends and family that the guy on Facebook she has talked with over the past 2 years, IS HER FATHER. Not sure if her husband or kids kow about me. She is very protective of them. I am thinking her Mother suddenly was told and said to keep away. I can only guess. I need ideas. She works with the legal system and many know her.

My only advice is to back off and wait patiently. It does sound likely that someone convinced her to stay away. With hope maybe the truth is being investigated by someone she works with rather than just believing her mother. Modern paternity tests will be definite but she would have to agree to one, and again, I would wait for her to contact you.
Since she is on Facebook... I assume you are too?? If not, that would be a wonderful way for her to learn all about you from a distance. Keep it current and not too specific; friends, family, pictures, etc.

I think you play it low key, and follow her lead. Whatever you do for now, don't push. She will make up her mind eventually, but it will be in HER time, and HER way.

I'm curious as to why a court told you to stay away? Unless you were shown to be a danger to the child courts are not likely to do so. So there are aspects of this you aren't telling us.

Yes, unless you were a danger or threat courts do not tell you to stay away, so that may be a worry,

But after that many reunions don't work like the wonderful ones shown on TV. Many turn out where a child or parent does not want anything to do with the other. It may have been safe while on email or Facebook, but backing out on a real meeting is really common.

Just be there, don't push too hard