I was unable to acquire Shiver Armor for my level 12 Sorceress. Every level since level 12 it was still red and unavailable.
At level 16 I tried again and it was still unavailable. I then went to my inventory and un-equipped my +1 Ice blast sacred globe; hit “R” to switch weapons to my Axe of frost (no shield); and only then was able to acquire Shiver Armor.
I had Frozen Armor binded to “LT + B”. Maybe that caused the issue (or other spell bindings. I didn’t have any spells bound on the weapon swap.