Oh- maybe there's a misunderstanding? It asks you to buy 4x Bronze I Packs. Not a single pack containing 4x cards. You just have to buy the very first pack 4 times.
Yep, that would be it. I though you had to buy a x4 pack, which the game does not let you buy despite having the money. Before going inside the menu, you have 500$ which means you might assume you will not have enough for 4 packs of x3. This is why I did not think this is what the game was asking. Maybe you should make it so the cost shows "Free" instead for the first 4 packs required for the tutorial? Maybe even with a indicator going down each time you "purchase" one until it reaches 4?