First of all, this should be an extremely rare event, but it is possible. If you are the unlucky one that this happens to then the first thing to note is don't panic. Your money is safe.
If you have given consent in your bank app to transfer your money and the money has not moved the first thing to do is check with your bank. It could be that your bank has taken a precautionary measure to delay payment, if that is the case they can explain to you why they have done this.