You are using a Mastercard BusinessCard where withdrawals are not permitted. You are using a Visa card issued in a country or from a creditor where withdrawals are not permitted. You have not met the requirements of the closed loop policy.
For this reason alone, Betfair has no reason to ban or close your account when you should win. This is what Betfair first became famous for; peer-to-peer betting. Whilst the Exchange account won't be closed for winning, there is an additional commission rate.