I've been using the Cashrewards notifier for months now without issue. But over the last couple of days it hasn't been detecting web sites when I go to them (like Amazon & Myer).
Also, if I click the notifier icon it displays an empty "Featured Offers" tab (just the three pulsing dots are shown).
This happens both on my home PC and work PC.
On Chrome version 74.0.3729.169.
Have you uninstalled and reinstalled the extension?