A returning client is not a new client
A client who has been away for three months, or a year, or six years, walks back through the door carrying something a new client does not have: a history with this work, and a story about why they stopped.
The instinct, when a familiar face returns, is to pick up where the lessons left off. The honest reality is that there is no such place; the client is not the same player or musician they were on the last lesson before the break, and the coach is not the same teacher either. The first lesson back is its own thing, and treating it as the next lesson in an old sequence is the most common reason a returning client does not stay.
A coach who handles the first lesson back well tends to keep the client for a long second run. A coach who handles it as a continuation tends to lose them again within four or five lessons, often without ever knowing why.