Double Tap
Send this a few days after a check-in email to bump it back to the top of the inbox. It reads like a quick personal follow-up: one line asking what's getting in the way, with your first message quoted underneath. Paste in the exact text of your earlier email, keep the same sender name, and skip contacts who have already taken the next step.
Loops
Keep it a real follow-up
Send it from the same name and reply-to address as the first email, and quote that email word for word so the thread holds together. Add a timer of a few days after the first email in the same Workflow, then use an audience filter to skip contacts who already did what you asked. Keep the formatting plain, with no images or buttons. The plain-text email entry covers when that style works best.