I am starting to use the jqGrid however, to be beginner, do not work properly.

Please ! Help me!
When the page is loaded, the data of the grid are not shown. Only after clicking the Refresh button is that the data of the grid are displayed.
Someone I could explain what might be wrong? How can I fix this? I would like to data from grid to appear to load the page, as well as work for examples. PS.

PS. I am using json datatype.

Thank you very much!