Perhaps you have already solved your problem. If not, I hope this helps.
The plugin definitely works in Storefront.
You have set to Enable on the general tab. You also need to set to Enable for all or any of the other tabs, depending on which stickers you want to enable.
If you want to use the New Products sticker, click on that tab and choose your desired settings. You then must do the same for On Sale and Soldout if you want to use them.
For example, I only use Products on Sale and Soldout, so I have enabled and configured those (including uploading a custom image- a great feature!). But I have not enabled New Products.
Once you enable the specific Stickers you want, I’m sure you will have no problems.
Cheers
Stephen
