Do employees first have to participate in an engagement survey to get an invitation to a follow-up survey? What about new employees vs. those who’ve simply changed locations?

No. Every currently eligible employee is invited to each engagement and follow-up survey, whether or not they took the last one.

Eligibility is based on time with the company, not survey history. A new employee joins the engagement and follow-up surveys once they've been with the company 100 days; before that, they're in the new-hire journey. An employee who moves to a different location keeps their company tenure, so moving doesn't restart them or change when they're eligible.

Read more in About Engagement and Follow-Up Surveys.