Where do I see the late-cancellation fees players owe me?

In two places, depending on whether you want one game or the whole picture. This is for late-cancellation fees only: players who simply have not paid for their spot are in the “Debtors” tab next to “Fees” (your own profile in “Game Creator” mode, “Restrictions”, “Debtors”), not inside a game.

Inside a game, open “Manage”, then “Payments”, and switch to the “Fees” tab next to “Payments”. It shows everyone charged a late-cancellation fee for that game, grouped into not paid and paid, with the payment date on settled ones.

Across all your games, open your own profile in “Game Creator” mode, tap “Restrictions”, then “Fees”. That is the full list of late-cancellation fees players owe you, and where you cancel a fee to let someone off, including one already paid, which returns the money to them.

A fee for a cash game reaches your balance only when the player actually pays it, because cash never passes through Playbox. You are notified the moment they do. Until then the fee closes your games for that player, whatever method they would pay with: settle first, then join. If nobody pays, the fee expires 60 days after the cancellation, so an old fee never blocks a player forever.