Hmm, do you have the armor files in all the right places?
You need the entity folder for teh armor in the entity/inventory/equipment/ folders. There you put body/<armor entity folder>
Also, in the set/stuff/body folder goes a file for the armor as well
{from "pattern overcoat"
{tag "armor"}
{inventory
{size 2 3}
{weight 100}
}
{desc "New_armor_can"}
{entity "new_armor_can"}
}
Thats what the file in the set/body folder should look like. That is my file, the desc and entity part should match the name of the entity file.
THe final place to look is in localization/desc and in there at the bottom under {"small_stuff" or w/e its called, you should add in your case
{"my_armor" "my_armor"} the 2nd "my_armor" can be anything you want.
THe 1st is the files in your mod folder, the 2nd is the name that will display in game. So, {"my_armor" "Heavy Flak Armor"} In game, you would see Heavy Flak Armor as the display name for your gear.
Once all the files and folders are in order it should just work.