Probably you don’t have enough commissions for the payment.
In order to receive the payment, you need to have available balance that is not less then 100$ or equal to btc.
Another reason could be the lack of payment method in earning currency. For example, you earned 0.05 btc, and indicate USD withdrawal method. In this case payment can’t be done to you.
We highly recommend to fill in BTC and USD payment methods. You can mention USD payment in your BTC wallet.