Lkwd mom:
Just want them to try again??
I thought the intention of your original question how to show them appreciation for their time,effort and thoughtfullness on behalf of your child whom they owe nothing to and put forth a great deal of energy for.
I guess I misundersood.
Here’s a secret, shadchanim are far more likely to stay in contact with you if they sense you trully appreciate their efforts, it is far more than if you attempt to “buy them”.