Voidic Protection advancement currently doesn't get triggered via the Ichor or Astral armor sets, but does for all 3 previous tiers. Either update this so only the Voidic Set (as it's needed for the later tiers anyways) or for all sets to trigger the advancement.

to clarify, this issue is as of 1.5.294

it's a bug, ichor and astral are supposed to trigger it.