It sounds like the File > Page Setup > Page > Paper Size selection has not been set correctly when you had created the Form Name in Printers and Faxes > File > Server Properties.

Look at the form name you had created and review the Form Measurements with a ruler to your checks.

Once the Paper Size has been selected in the template and the template is saved, the Form Measurements are used by Excel to print.

You did create the form name on machine where the printer is attached to and can select the form name from File > Page Setup > Page?