Have a current run in Arena as warrior. For some reason my hero power stopped giving me 2 armor when pressed - took the 2 mana, but got no armour. The actual shield icon on the hero power also was missing / didn’t renew.
This basically cost me the game as my spells and battlecries that did damage equal to armour plus lack of benefit from that armour.
Did you at any time during the game play the Supercollider?
https://hearthstone.fandom.com/wiki/Supercollider
There is at this time a known visual bug where the armor is not displayed in the right position after attacking with supercollider, and often that incorrect position is even literally off screen. The armor is still tracked correct internally, but not visible on the screen.
I did have supercollider - but it wasn’t tracking my armour. As I had several ‘do damage equal to your armor’ which did nothing after pressing the armour button, also the next turn when hit by the enemy I lost health equal to the minions attach (no 2 point reduction for the armor just activated.
It’s been buggier than usual lately. In my last game just then my opponent played Raid Boss Onyxia from Drakefire amulet and it was immune, and stayed immune, despite there being no Whelps on the board.
I only play occassionally and I have seen one bug or another in 4 of my last 6 or 7 games. I’ve been playing for many years (I think 5) and never seen it this bad. Hopefully when it is upgraded for new release it will just fix a lot of it.