We want to order online and use my military discount

You need to use the Military and Veterans store.

See here: Veterans and Military Store - Apple

Apple discontinued the 256GB version of the XR in September. They currently only sell the 64GB and 128GB version in the store.

If anyone is still selling the 256GB version and dropped the price, it was not Apple.

The Veterans and Military Store offers a flat 10% discount on all products.

Recently, Apple dropped the price of the Iphone 11 pro with 256 GB for $1149 on the regular retail site. I found out about the military discount and registered today. However, the price is exactly the same. I'm wondering if they just haven't updated the military site or I have to do something additional? Thanks