Sort Order products by price within category

I am running on zen-cart 1.27 and want to sort my products by price. low to high.
I have set the Display Product Listing Default Sort Order to 3a in Product Listing but is not working.

Display Product Image 1
Display Product Manufacturer Name 0 Informatie
Display Product Model 2 Informatie
Display Product Name 2 Informatie
Display Product Price/Add to Cart 3 Informatie
Display Product Quantity 0 Informatie
Display Product Weight 0 Informatie
Display Product Price/Add to Cart Column Width 125 Informatie
Display Category/Manufacturer Filter (0=off; 1=on) 1 Informatie
Prev/Next Split Page Navigation (1-top, 2-bottom, 3-both) 2 Informatie
Display Product Short Descriptions 4 Informatie
Display Product Listing Default Sort Order 3a

PLEASE HELP:wink2: