I have multiple customers in Clover, but none are syncing with ListBuilder. Why?

Even if you have customers in your Clover account, they won't sync to ListBuilder unless they (1) have a valid email address and (2) have opted in to marketing via ListBuilder.

Note: Opt-in must happen through ListBuilder — customers already in Clover before you set up ListBuilder won't sync retroactively, even if they meet both requirements. See How can I get customers to opt in to my email marketing from Clover? for guidance on collecting opt-in.