Silence almost never means no. It means buried, busy, forwarded-and-forgotten, or "meant to reply on the train". That is why the follow-up - not the first email - is where most replies actually happen, and why the worst thing you can do is make the recipient feel guilty about the delay. Every template below is written to be easy to answer in ten seconds and impossible to resent.
The craft is in escalation: each touch should be DIFFERENT, not louder. First a two-line nudge in the same thread. Then a message that gives before it asks. Then a genuinely new frame - a customer story, a different pain point. And finally a breakup note that closes the loop with grace, which regularly outperforms every message before it. Fill the [placeholders] with specifics; the specifics are what get answered.