Hi sunlye,
If you just enabled the automatic feedback setting after receiving my previous message, it would be expected for the system to not go back and leave automatic feedback messages for transactions you have already received positive feedback for. However, the system should automatically leave feedback automatically for any of your transactions for which you receive positive feedback from that point on.
If the automatic feedback system has not been working in this manner, we would need to investigate that occurrence further. In that case, I recommend contacting our customer support team by mousing over the "Help" tab and selecting the "File Support Case" option.
-Mike