I purchased the Platinum Angel style during the Daily Deals a while back. But the style is not in my collection. I know how styles work. This is not about having the wrong card or not having the card or anything like that. The style itself is not available in my collection. The others I bought that day are all available.

I am having the same issue as I got the retro style as the free anniversary skin, but cannot find that style any where. I told my friend on discord with a screenshot so I know I obtained it on 9/19/23, but I cannot find that style anywhere. I checked both the brother's war and the M10, but I could not find the style under either of them.

i craft both version m10 and brothers war still cant apply skin

The styles can only be applied to the cards from the specific set. Your Platinum Angel is the M10 version (Historic Anthology 2), while your card style is for the retro artifact version of The Brothers War subset. You either need an M10 card style for the Angel you already own, or you need a retro artifact version of the Angel from Brothers War for your card style.