Troubleshooting Create Shipping Label
Issue
White screen stuck on "Please wait...Sending data to print..."
Cause
Newer browsers do not support NPAPI plugins i.e. browser security is getting more strict.
More than likely NPAPI is no longer supported if you are using a newer browser and NPAPI is what is used to allow the browser to communicate with your label printer. Below are some workarounds that will allow communication to flow smoothly.
Temp Solution (only works with Firefox)
source/reference: http://www.omgubuntu.co.uk/2017/03/force-enable-firefox-52-npapi-support
Open firefox and paste about:config in address bar
Add new Boolean string "plugin.load_flash_only" and set it to false
restart the browser