One of my restaurants stopped paying. Am I out of pocket?

No. A line is only ever made from a month a restaurant ACTUALLY PAID FOR, so a restaurant that stops paying simply produces nothing that month, in either direction — you are never asked to fund a customer we were not paid by, and a signup that never becomes a paying restaurant never becomes a line either. It also means the earning is not a one-off introduction fee: a restaurant you set up two years ago still produces a line every month it trades.