I’m sorry for your predicament jp1692. The only thing I can think might work at this point is to stop trying. If you are periodically contacting them, then each time you try to contact them they are confirming in their own mind their decision to shun you, and it gets lodged deeper and deeper. There is a sunk cost fallacy too, where each instance of shunning becomes more costly to overturn because of all the previous investment in shunning. So perhaps it would be good to remove the opportunities for them to actively shun you by stopping contact. It may just give them enough space to wonder, reconsider, and react differently sometime years down the line. (In order to make them wonder it would be important not to announce it either, saying “this is the last time I’m going to contact you, and I hope you stop and think about it”, but instead abruptly halt attempts to contact)
I’m sorry there are no good solutions in this situation.