The top reasons why Cross Sell might not be working properly, and/or your cross sells might not be showing are:
1) Our Cross Sell snippet is not installed properly on your theme's product and/or cart template. To verify that our snippet is installed, read this article.
2) You have selected products as cross sells that are not published on your store's online sales channel. Cross sells for your products NEED to be published on your online sales channel to work.
3) Cross Sell is stock aware by default on v1 (this can be turned on/off by us if you're on v1, or by you in Settings if on v2+) which is why out-of-stock cross sells might not be showing up. If you want to turn this feature on/off in v1, please contact us.
4) If you have for any reason changed a product's handle and that product had been selected to appear as a Cross Sell item, then that item will not show in your store’s Cross Sell items. This happens because the link for it had been made with the old product handle and therefore it is looking for a product that no longer exists.
To fix this, follow the steps outlined here -> https://help.csell.co/a/solutions/articles/3000077421
We also have a video here -> https://vimeo.com/278292336
We are aware that adding cross sells again is not ideal, and are working to re-engineer the app so that any change of product handle will be highlighted and you will be provided with a mechanism to swap out the old product handle for the newer one.
5) Similar to the above, should you import a set of new products over the top of your existing products, and you have renamed them with new product handles, then the link with Cross Sell will be lost.
6) If you are clicking on the 'View this product in your store' link from within the app, and the Cross Sells are not visible when your page loads. Please perform a 'hard refresh' by holding down ⌘ Cmd (Ctrl on Windows) + the ⇧ Shift key + R. Your page should then refresh with the Cross Sells now visible.