I just can't seem to reach act 4

I'm new to the game and new to the whole genre.

I don't make any huge mistakes outright, but I seem to really suck at the game even so.

This is the second time (out of 6-7 run attempts) I've reached the act 3 end boss and can't get past it. The other good run was with Regent. This time I'm using Ironclad.

Look at this crap: https://i.ibb.co/bgq4Q5N9/act3boss.jpg

I'm on the third phase of the Test Subject fight and I receive no block cards at all when I need them. I've already used my potions. I just get attack cards while the boss is invulnerable. What am I supposed to do with this? I've already Saved And Quit and re-tried this fight with almost exactly the same result. :(