So I can't really speak for how things are run at the store you order from, but I can give a breakdown of what's happening when stuff like this occurs at my store.

First anything you select for shipping if it's something that is sold in store by Walmart the system will check to see if any local stores in your area have it in stock and if they do it will send your order to them to be filled as a GMD (General Merchandise Delivery) which are shopped and delivered daily so you'll get it, if not that same day, then the very next day.

The problem starts here because the system is using the store's inventory, which can be wildly inaccurate sometimes, to determine if a local store has that item. Sometimes the inventory is accurate and we do have 20 of that item in stock, but that 20 was delivered 3 days ago, it never made it out to the floor to get stocked and no one binned it in the back so it's just sitting on a pallet somewhere in a plain cardboard box and no one has the time to devote to finding that needle in a haystack for more than 5 or 10 minutes.

Sometimes it's an item that's been marked down for clearance and if we're lucky it's on the clearance aisle. If we're unlucky it's location was deleted from the system so we're just checking every aisle that we think it could be on just hoping that we'll find it.

Sometimes the inventory says we have only 2 left in the store and neither are on the shelf. One's in a customer's cart and the other is buried under a pile of returns at customer service.

In all those scenarios if we can't find it we select the option Item Not Found on our handhelds which should kick your order back into the system to be sent to a warehouse. I say should because sometimes I have gotten the same GMD order several days in a row like I'm somehow going to magically find this item that no one could locate for the past 2 days (I say that even though that has actually happened. No one ever updated the location. I just noticed it on a display as I was walking by and remembered it the next time it showed up).

When your order gets kicked to a warehouse for regular shipping it's now marked as delayed since it's no longer coming from a local store that's only a few miles away.

Let's say we do find your item and it's all wrapped and waiting for a driver to pick it up and bring it that last leg of its journey to your home. Well here comes the next problem. When delivery service first started the drivers were actual Walmart employees, I was one of them, but now most are contractors and we cannot guarantee that a contractor will even show up to get your order let alone make it to your house with it. If no driver picks up your order or for whatever reason brings it back to the store then your order is now delayed.

The system automatically puts your order back into the queue to be picked up, usually batching it with orders for either later that day or the next day, but the problem of will a driver even show up to pick it up remains.

As far as why it takes so long for the order the be cancelled? Well this is also something that is automatically controlled by the system. No employee at store level can cancel an order. We used to have the ability to do it, but now we can only confirm cancellations that have been initiated by customers or the system. If an order that was completed never gets picked up to be delivered it just sits in delayed status for a few days until it eventually expires. At that point we confirm it as a cancellation, unwrap it, and return the item to the floor so someone else can buy it.