Hippo Charging is here to help in every way possible. Upon boarding your account we turned on a security feature that does not allow for two transactions of the same amount to be charged within 15 min of each other.
This is done to protect you as a merchant. Sometimes it is a mistake and this prevents chargebacks. In other cases you may sell an item that is the same price and this may cause a problem. Please let us know if you would like this to be turned off, or need a better explanation.