I did a search on the interenet and this stood out:
Quote
Just go straight ahead and get the matter before a judge as soon as you can. Don''t waste time and money trying to negotiate with someone who refuses to engage with the process.


I am thinking something like this:

H"W, When you say you want a divorce, but then refuse to negotiate, I feel frustrated. Negotiation is part of the divorce process. I have given you my proposal. I expect a response by (this date). If you do not respond, I will petition the courts asking for mediation. Thanks for your attention on this matter."


I learned that giving the other person two choices (both of which I am fine with) works well.


"What is best for my kids is best for me"
Amor Fati
Link to quotes: https://www.divorcebusting.com/forums/ubbthreads.php?ubb=showflat&Number=2879712