First, no worries - should things not work out, you can always access your label from the "History" page.
That said, to fix this issue you will need to go thru this article:https://helpx.adobe.com/acrobat/using/display-pdf-in-browser.html
If it still does not work, then you will need to troubleshoot, and we have found this article to be the best:
Bottom line - Adobe Acrobat Reader needs to be installed... and active inside the browser.
The other option is to switch to Microsoft Edge or Google Chrome (recommended).
If we find other solutions, we'll update this article.