In Increased Armory: Pacific, you are not able to respawn with vests. This is intentional, as you wouldn't be able to stop respawning with these wearables otherwise. The wearable item slot on your character namely starts working like the other slots when making vests respawnable items.

If you prefer, you can make vests respawnable locally.

Navigate to

Then open all *.carry_item files in this folder (except gold_bar.carry_item) and find the first instance of the following parameter in each file
Simply replace 0 with 1 and save your changes.

This will make all vests "non-blue" items, meaning they can be respawned with.