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 bring in any listings recently added to your store, but not yet imported into SKULabs.
If this doesn't work, check your listings tab for any which can be manually linked or relinked.
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, edit the order on your sales channel to correct the item, or change your store's custom line item policy.
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.