Show as icon not working

Dear Bert,
I'm finishing off an overview sheet that averages scores across several tabs. I want the number to be represented by number icons so that it is easier to see at quick glance.
On the test mark book, it worked perfectly, but on the final version of the workbook, it doesn't seem to be working properly. It is showing 0 as an icon fine, but as soon as the number changes, the cell is empty.
I have attached the mark book. It is the APP sheet that I am looking at. The first set of columns is the average calculation column. The second set of columns is where I am trying to represent the number as an icon.
I have set up the icons as a grade so it should all work ok.
Would you be able to have a look and see what is the matter please?
Password is just password.
Thanks
James

Managed to get it working. Had the wrong grade type in source cell.