This error occurs because the balance calendar does not include periods beyond the current one. To fix this, please follow the steps below:
Navigate to WFM Admin Dashboard, then select Configuration.
Search for Balance Configuration and locate the balance in question.
Click the three-dot menu next to the balance and select View/Edit Balances.
Go to the Balance Calendar tab.
Click Add Period and enter the new period number.
Input the Start Date and End Date, then click OK.
If necessary, fill in the End Period Limits (Days and Hours).
This will extend the balance calendar and resolve the error.