Your redeem order might have failed due to one of the following reasons :
Your scheme does not allow you to redeem (sell) units below a certain amount. In this case, please read the scheme details once.
You have invested in ELSS funds or retirement funds and the units you are trying to sell are still in a lock-in period.
The units you are trying to sell are yet to be allocated to your account. Once the purchase order has been placed successfully, it takes up to 4 working days for the units to be allocated. Sell order can be placed only after you are able to see the units allocated in your MF dashboard.