Firstly, DO NOT panic, your funds are absolutely safe.
There could be one or more reasons depending on the situation as follows
You must've entered the wrong MPIN
You must've entered the amount outside the withdrawal limits in single transaction
Bank account is not linked with your Nuo Account
There might be technical issue from the payment gateway provider
In case of any maitenance services from payment provider, the withdrawal service might be affected for sometime but in most cases it is pre-informed and takes place in the non-business hours.
In case you face an issue while withdrawal, reach out to us via "Talk to us" option in the profile section and our team will resolve the issue in 24-48 working hours.