There is no data displayed in Hazmat Information panel for a Hazardous item. 

Answer

Hazmat Information is displayed in the panel only when a value is entered in the Hazardous Material Class field and the "Is Hazardous Item" checkbox is selected for the Hazmat item. Depending on the validity of the Hazardous Material Class field, the Hazmat Information Panel is populated. If Hazardous Material Class field is valid, data is populated or else the Hazmat Information panel is left blank.

Even if configuration is correct and Hazardous Material Class is valid, the Hazmat information is not displayed. Why?
The Hazardous Material Class provided for the item is not mapped correctly. It might have been created with the name of the Hazardous Material Class. Hazmat Class in the product is mapped to the SORT_ORDER column in the yfs_hazmat_compliance table (not the description). SORT_ORDER is Unique number to identify a hazardous substance.

How to solve the above problem and display the Hazmat information?
Create a classification with its value equal to the SORT_ORDER value of that Hazardous Material Class. Once you chose this classification as the hazardous material class for the item, the system displays the data in Hazmat Information panel.