[2021] Why can’t I swap out, or even activate, my shield?

I don’t know what is going on, but since yesterday, I can’t swap out my shield for a different skill, because the shield is on always cool down, somehow. Right now, my shield is grayed-out and I can’t use it at all, which is not great, and it’s been that way for five minutes now.

Playing on Heroic, with Ragers and the ammo directive active, no skills directives active, ever.

Is this a known bug that I’ve never seen before?

Edit to add that now I’ve got a broken room with no combat, and 2 active separate objectives in the next room, and still no shield.