After the Wilds update it seems there are some problems with chest shops.
Some days after the update, someone came to buy wool from the chest shop at my visit, and it didn't work. So I tried re-creating the sign, but no dice.
As an experiment, I went to Emerald City (where I am an assistant) and tired it there. Worked like a charm.
I've heard from others that they've had problems too. I'm wondering if it has something to do with the chest ownership permissions between town and Wild....in towns you are explicitly the owner, and each chest is created as a private chest, whereas in the Wild it's sort of automatically owned by the landowner (inherited permissions maybe?)
Anyway, would really love for this to be fixed, and am probably not the only one. Let me know if you need any more information.