Update! Walmart app is reportedly working much better than the website. If you have trouble getting it through their site try their app. They keep restocking these every few seconds so keep trying. If it says "This item is momentarily out of stock" that means keep refreshing and it will pop back up.
PLAYSTATION 5 AND XBOX X RESTOCK at 3PM Eastern, 2 Central, 1PM Mountain, 12 Noon Pacific! In the past they have had more restocks every 15 minutes for another hour or 2 after the first live time. Not sure if they will do that now but if you miss the first wave keep checking back at 3:15: 3:30 etc... The page will let you know if there are more restocks coming
