Suddenly I can't print the labels anymore and have to select the option to open it as a printable web page. Anyone know why this might be happening?

Perhaps your pop-up blocker is getting in the way? Here are some suggestion from the Help Center:

I can't print my wrapper!

If you are having trouble printing your wrapper:

First things first:

• Check the ink levels in your printer.
  • Some printers will not print if the ink is low.
• Make sure that your printer is able to print other documents.
  • Print another document that is on your computer's hard drive, to test the computer-printer connection.
• You need Adobe Acrobat Reader to handle the downloaded .pdf file
  • this is a FREE application, available for download here.
  • If you do not want to download anything, just use the 'backup wrapper' link on the Wrapper Settings page - this will show the address in a printable webpage and skip the download completely.
• If you have Adobe Acrobat Reader already:
  • make sure that it is not corrupted, and that you have the latest version.
• If you are using Internet Explorer, you should consider downloading Firefox.
  • Firefox is a much more stable and secure browser than IE.
  • You can get FireFox, a FREE browser, here.
  • Firefox is the preferred browser for the PBS Team and it offers the best experience navigating the PBS site.

Then:

• Make sure your popup blocker is disabled for the PBS site (there are no popup ads at PBS, so this is safe).
  • you can do this in your browser settings
• If you continue to have trouble, click the Backup Wrapper Link on the Wrapper Settings page. The "backup wrapper link" = the "click here" button to show the address in a printable webpage.
  • This will open a printable webpage with the address information on it.
• Check the "estimated weight"  on the Wrapper Settings page. 
  • If the estimated weight is crazy (like 20 pounds!), contact us to let us know the ISBN and title of the book(s) in the shipment and we will correct the database.
  • Our database is compiled elsewhere and does have some erroneous/missing information for book weights.  If the database estimate of the weight is too high, the wrapper won't print.  This needs to be corrected manually, by us.
• If you are running Firefox with an extension called "NoScript" read this: NoScript and PaperBackSwap
• If you keep seeing a message telling you that the page is not loading completely, read this: Configure your browser to work with PBS

Full instructions for printing the PBS Wrapper are here.

Every now and then the postage provider is down, for their back up and changes.  If that is the case, then they are usually back up in half an hour or so.  We don't get warning, it just does not go through.