The most likely reason is that your label is not properly formatted for 4 x 6 label printing. SP410 prints exactly what you see on your printing file in the same orientation.  So if it has a lot of white space around the label, the printing will be side-ways. 

Check if your shipping platform can provide 4 x 6 labels in the correct orientation. We have How-Tos for the most popular platforms, here is link: http://www.idprt.com/prt_v2/other/question.html

For Windows:

Go to Control Panel -> Devices and Printers -> Right click on “SP410 Printer”-> Printer preferences -> Page -> Under “Rotate” choose 90°and Apply Click Ok.

For Mac:

In the file Print window, select the size under ''Paper Size'' and then select 90 under "Orientation".