Leave taken deducts from wages but does not add a leave quantity

If this is the case, you'll see behavior similar to the below:

Before Pay is taken, we see 0 days Taken.

After the Leave is taken, we see a Leave value deducted from the Ordinary Wages code:

However, the Sick Leave taken does not go up, and we cannot add it manually because the Quantity is uneditable.

This normally indicates that the Employee's Work Schedule does not include the days they are taking as leave.

Check the Employee Work Schedule screen:

If the Employee Work schedule screen is empty, then we need to check if the Employee has a Default Employee Pay Group:

If they have a Default Pay Group selected, check that the Calendar specified is configured correctly to include the employee's working days.