Hi.
How about your database, is it still being updated today? If not, then my guess is that XML provider has probably changed their XML structure for 2016, and so the XML-PARSING section inside your PHP code (cron job) might need some adjustment.
If it is still, then maybe that PHP code halts somewhere in middle and thus not executing email sending section. One possibility is recent PHP upgrade to version 5.5. This version might naturally generate deprecated errors, when your PHP code is still using mySQL_ functions. If true, then I guess you need to convert those mySQL_ to PDO.
Other possibility I could think of is recent server upgrade. It may stop current running cron job. Have you contacted your host provider about this?
Kindly let me know more details, should you need me to further investigate this:
(a) URL to XML feed.
(b) your PHP code (activated by cron job).
Hendra D.