The preview notification feature doesn't work as expected in Orlando for one of the custom tables. Typically, it should select a record when you click on Notification preview and then preview the email by loading the data of the selected record.
After upgrading to Orlando, the body doesn't populate any content when the Notification is previewed and when a record is selected
Found the record display field value is not seen under preview field when the Notification preview is clicked. But still if you select any of the records from the preview field, the data still doesn't populate in the body.The issue is with the display field on the table
If a field is selected as a display field on the table, make sure this field has a value on the records. This is when the preview gets populated with the actual content in the body based on the record data.
Make a note that actual email still holds the values for the email body though the display field is empty for a record. It is just the Notification preview that doesn't populate the body content.