When using bulk actions or if you are in user's planner, the system won't accept entries in the planner over public holidays as this is how it's designed to work.
If the public holidays are included in their entitlement, you can turn on this option:
Click Access Button
then click Employee.
Select a relevant employee then click Planner.
Click on blue Settings button then tick Entitlement Includes Public Holiday.
If you include public holidays in their entitlement, add the number of public holidays in the year to the employee's entitlement. Then any public holidays that land on a working day for that employee are automatically booked from their entitlement.
If you don't include public holidays in their entitlement, the employee is still on a public holiday template. This will simply display as a non-working day for an employee and will not affect the entitlement.
📌Note: When employees have public holidays included within their entitlement, the duration of the public holiday will be set to 1 by default. When you change the public holiday duration to 0, a day will get added back onto the employee's entitlement.