Hi Jim...
I'm in a similar situation. Found my bmom...she's 71 now. Wrote her a letter with a stamped self-addressed return evelope. No reply. Sent a card...no reply. Eventually called on the phone. Confirmed it was her and told her my name. She hung up .
When there is no reply youimagine all sorts of things...most of them are probably nowhere near what is really going on. I eventually called her sister whe had no idea I existed. We talked for a long time and she filled me in on some family history that helps her "no reply" to make more sense in my head. I'm going to wait a while and try again.
Thats all you can do...is be gentle and try again....until they kick you in the teeth!
Good luck