Missing listings are a side effect of orders which contain or used to contain items that SKULabs has not received in a listing sync from your channel. You have several options to resolve this either on your store, or on SKULabs.
Run a listing sync for the affected store to see if the item has been added recently and just needs to be imported.
If this doesn't work, check your unlinked listings if there are any which need to be linked.
If this still doesn't work, check the order on your sales channel to see if the item was the original product or variant was removed, replaced, deactivated, changed, or deleted altogether directly on your channel. If so, either reactivate the item or edit the order on your sales channel to change the item that should be included on the order, then re-sync your orders to fetch the update in SKULabs.
If you have BigCommerce, this is a common issue when you have customization options for line items, and you will need to specify those custom options into your BigCommerce store settings.
Also read our guide on troubleshooting missing listings.