Cannot use coupon after upgrade to Prestashop 1.6
Are you saying that the voucher works sometimes and sometimes does not?
Can you also verify the overrides? It can be found here:
Lastly, if you are seeing the error "The voucher does not exist" then AwoCoupon is not being called at all. This is the default error message for Prestashop.
On a test server I have:
- Smart cache for CSS: yes
- Minify HTML: yes
- Use cache: yes (file system)
And coupons are still working fine.
Maybe you can debug by only testing one of the performance parameters at a time, and see if there is one specific causing the problem?