First, check if you have a sufficient balance in your Wallet at the time of the scheduled transfer. If the balance was insufficient, the money cannot be saved in your Piggy. In case the current balance in your Wallet is now sufficient, then a new attempt will be made on the next scheduled date.
If the problem remains, you can open a support request using the yzy bot, in the 'Help & Support' section located on your profile to help you.