1. Technical failure: There is a technical failure in the payment system of RT Mart parking lot, which prevents you from completing the payment. You can try to solve the problem by other payment methods (such as cash) or contacting the parking lot manager.
2. Preferential activities: RT Mart parking lot is carrying out preferential activities, such as free parking time or other concessions, and there is no need to pay parking fees. For details, you can consult the parking lot management personnel or check the relevant announcements.
3. Misunderstanding or mistake: Due to misunderstanding or mistake, the parking fee is shown as 5 yuan, but it is not actually necessary to pay this fee. You can read the charging policy of RT Mart parking lot carefully again, or ask the parking lot manager for the specific parking fee.