How to apply Artificer Armorer level 9 Armor Modifications?

I have just hit level 9 and I am an artificer armorer. Armor Modifications states:

"At 9th level, you learn how to use your artificer infusions to specially modify your Arcane Armor. That armor now counts as separate items for the purposes of your Infuse Items feature: armor (the chest piece), boots, helmet, and the armor's special weapon. Each of those items can bear one of your infusions, and the infusions transfer over if you change your armor's model with the Armor Model feature. In addition, the maximum number of items you can infuse at once increases by 2, but those extra items must be part of your Arcane Armor.

I currently have splint armor and do no be able to make it specifically "arcane armor" in the app. Nor do I seem to be able to apply more than one infusion to it. Does anyone know how to do any of this?

I also do not seem able to infuse my "Thunder Guantlets". For whatever reason, they show up under my actions tab but not in my inventory. Does anyone also know how to do this?

Thanks

I have the same issue ... It has been on since 2021.

It's pretty much the only thing hapenning at level 9 and it's just not usable ...

I'm looking fot that too.... 

Since this is something that's only applicable to the 5e version of the Armorer subclass, I wouldn't expect to see it fixed anytime soon. It's unlikely they're going to spend any effort on 5e-only features at this point.