The fulfillment lag time you submitted exceeds Walmart's allowed maximum of 4 days. Listings with high lag times are demoted or hidden from search.
Lag time is the days between order receipt and shipment. Walmart caps it at 4 days for most categories and 0-1 days for items advertised as Two-Day or Next-Day. High lag times correlate with poor on-time delivery, so Walmart penalizes them with reduced visibility and Buy Box loss even when the value is technically accepted.