Make sure you are on the actual computer you would like to test the printer for and do the following:
Navigate to your event calendar
Click on the drop down menu in the top left
Select "Check Printer"
You can also go directly there via the following link. Replace <subdomain> with your account's subdomain.
You will be directed to a page which will perform tests to determine if everything is set up correctly for printing at the check-in station. Select the printer you are testing in the upper right (Dymo or Zebra). If all tests are green, then you are good to go. Otherwise, any failed tests will show the reason and how to fix it.
You can click on the "Rerun Tests" at the bottom to perform the tests again. If you are still having issues printing, please see this article for general troubleshooting tips.