I get that error when clicking on any category. Might want to get your website/database tech on that soon.
edit - and now it’s working. 
I just got the same error.
In a couple minutes
It just started working for me!
I noticed that their store is set up almost the same as andrew-amanda.com
I apologize, we had some technical issue which prevented the site from operating correctly, including the coupon code being rejected. Our IT staff has corrected the issue.
Thank you, JON.
So I did an order and had some issues and couldn’t use a code. Can I apply it retroactively?
Ah cool now you have joined the forum i can message Jetbeam on here instead of emailing!