I have Magento 1.9
I created a rule for discount 3 of my categories.
Immediately the rules works perfect, I see that everywhere sould be. But after a few time (I tried, but I didn't understand how much time or in consequence of what) the rules doesn't works good:
The rule work correctly on the catalog and category page (I see the discount), but when I go on the product's single page the discount dosn't work anymore.
The same thing when i go to the cart page or in checkout.
Pratically my discunt never work.
I tried to use the default theme, i tried to disable the plugin one by one but the problem persist.
This si an example:
CART AND CHECKOUT
Are you using some cache techonology? (Redis, Varnish or another one).