In the Projects+ parameters, under the Timesheets tab ‘Display balances’ checkbox is available to control this feature.
Go to Project management and accounting > Setups > Projects+ parameters > Timesheet tab.
Mark the ‘Display balances’ checkbox to enable this feature. By default this checkbox turned off. In order to use the PTO balances feature, turn on both the ‘activate personal time off’ and ‘display balances’ check boxes.