Hi X,
We’ve got an issues with our coupons. Some work, some don’t. And we can’t find a method to the madness.
We had a 20 percent off coupon to new subscribers but it stopped working (pronounce20) so we had to make individual coupons for frustrated customers. Those worked fine. We then made a new 20 percent off coupon (ps20) and that still doesn’t work. We have a general 15 percent off coupon uniquely generated at checkout (you’ll see the bluebox) and that one seems to work:
Here’s a screen shot of code ps20 always granting a 50 cent discount regardless of amount spent and it’s the same regardless of if free shipping or flat shipping is selected.

All Woo, Woo extensions and general plugins are updated. We planned to wait for the next release (after 5.2.3.) but if you can update the theme if you think it’s connected.
Thanks!