Why can't I see my Equipment in the Upgrade menu?
The Upgrade menu does not contain Equipment for your regiment, so you cannot upgrade items here. Here, you can only improve your regiments' abilities by applying upgrade cards.
Weapon, Armor and Banner items that are equipped by your regiments can be upgraded in the Forge. If you want to upgrade one of these, go to the Army menu and tap on one of the three icons at the bottom right of your screen. Here, you will see all of the items available for your chosen regiment, and those you can equip based on its level. After doing that, go to the Forge to check if one of these items can be upgraded, or tap on the Forge button in the highlighted item card.