For what I understand, as potency runes for armor and weapons don't have the invested trait, we don't need to invest them to receive its benefits.
Also, some property runes have the actavion entry. RAW, we need to spend 1 Resonance Point to Activate it. That's ok.
However, in Activating Magic Items entry (on page 376), we can activate only items that we have invested, as the Requirement entry says.
Requirement You can Activate an Item you’re wearing only if you have invested it.
Cost 1 Resonance Point, spent when you start taking activate actions for this activity
You activate an item’s magical ability. Activating an Item is an activity that takes a variable number of actions, depending on the item. The activate actions required are listed in the stat block. You can spend those actions in any order you wish, provided you do so consecutively on a single turn. As soon as all activate actions are complete, the item’s effect occurs. If an item has multiple abilities that can be activated, you must choose which one to use each time you Activate the Item.
Some items allow you to use an activate action as a reaction or free action. In this case, you Activate the Item as a reaction or free action instead of as an activity. Such cases are noted in the item’s stat block (for example, “ Focus Activation reaction”).
So, shouldn't those property runes with a activation entry have the invested trait?
It seems to me that you invest the magic armor, like every other worn item, and that one investment pays for any runes as well. If they put invested in the rune descriptions, that would mean having to invest each and every rune individually and that would be.... Gross.