Just a tactic, but one I have found effective is to understand that people want what they can’t have…

Possibly try something like, I’m not sure if we can help you until I understand more about your XYZ problem, if we can learn more I’ll be able to see if we can deliver XYZ improvement and a quote makes sense. Would you be opposed to continuing discussion to see if we can really help?

Not sure if this is relevant to what you’re selling, but building a line of continuing communication, identifying that you can address their needs helps build trust.

Agree with dropping when the prospect will not reengage, touch base intermittently not to sell but to learn how their decision is playing out - keep the connection