If you have selected Print Label and the print dialog box only appears as a blank screen before disappearing while using the Firefox browser, you will need to adjust the PDF options in the Firefox settings.
After selecting Print Label it may show a blank print preview dialog box, as shown below, before disappearing.
To change the settings, select the 3 menu lines in the upper right-hand corner, then select Settings from the dropdown.
Scroll down to Files and Applications.
Under Content Type locate Portable Document Format (PDF), then in the Action column to the right select Open in Firefox.
Your labels will now popup with the printing option at booking or when reprinting labels from the History/Track page.