A cancelled date is information, not a verdict. The reply that wins is the same either way: relaxed, gracious, zero guilt-tripping. How they handle the reschedule tells you everything.
The key signal: a genuinely interested person cancels with an alternative. No counter-offer plus vague someday energy usually means low interest.
No worries, things happen costs you nothing and shows security. Any flash of annoyance hands them an easy reason to bail entirely.
After one gracious reply, leave the reschedule in their court. If they want it, they will pick a day. If you keep chasing, you become the backup plan.
One cancel is life. Two cancels without a firm counter-offer is a soft no. Read it, stop initiating, and let them earn the next chance.
Keep it short and warm: no problem, let me know when works. Skip sarcasm and guilt. Calm is the most attractive possible response.
Interested people offer a new time, usually right in the cancellation text. Vague apologies with no alternative, especially twice, usually mean they are not feeling it.
Offer once if they did not. After that, let them carry it. If the new plan never comes from their side, take the hint and move on.