I found this in another thread and it worked!
Hello,
I understand that since upgrading to Mavericks 10.9, you are now no longer able to fax from the Mac. First steps that I do want to make sure of is that you have the most up to date drivers from Apple. I have included 'HP Printer Drivers v.2.16.1 for OS X', please click on the blue download button. Once the update has been installed, please completely shut down the Mac for one minute. After you turn the Mac back on, complete the following steps.
1) Click on the Apple icon
2) Click on System Preferences
3) Click on Printers and Scanners
4) Click on the plus (+) sign in the bottom left corner
5) Click on Default
6) Click on your printer with fax at the end of it
7) Click add at the bottom of the page
Please let me know if you are able to add the fax in, thank you.
Lil_Lisa27
I work on behalf of HP
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