The bridge from follow-up to conversation is a question, not a pitch. Attendees came for information, not to be sold to. The follow-up that gets a response asks about their situation rather than presenting a solution.
"Did the section on [topic] apply to what your team is working on right now?" opens a conversation. "Book a demo here" closes a door. You can include a CTA at the bottom of a follow-up, but it should come after you have delivered value, not replace it.
On timing: the direct ask belongs in the third email, not the first. Use the first email to deliver value (recording plus one takeaway). Use the second to open a conversation with a specific question about their situation. By the third, if they've opened or engaged, a direct offer ("happy to walk you through how this applies to [specific use case], does [Day] work?") lands differently than it would on day one.