What do the orange alert icons mean?

If you see an orange alert icon like the one below, it simply means that an upsell is missing a product or collection. This is usually because the product or collection was deleted from your store.

If you hover over the Alert icon, it will give you an overview of which upsell has the issue. Then, if you click into either on Page or Action Upsells and view your complete list of upsells, the same Alert icon will appear next to the upsells with an issue.

To resolve, either edit the upsell and replace the products/collections that were deleted or if you no longer need the upsell then simply delete that specific upsell.