Two possible reasons:

First, The most common reason is that your labels are loaded upside down. Please make sure that your labels are properly loaded with print side up.

Second, If printing came out blank, we may check if the media type is correct. SP410 is thermal label printer, please use direct thermal labels for printing. 

Here is quick way to check paper type:

Printer powered on, load paper, Press and hold feed button until green indicator light flashed once to release. It will print a self-check page. If the printed label is blank, we may confirm it is not thermal label. Please replace with thermal label and try again, problem shall be solved.