I have been using pinterest for nearly a year, white hat, not black hat.
Recently i started doing what OP adviced, i was copying the popular pics which are in my blog`s category (beauty) and put them in my site, then pin them from my site to my own boards.. At first days every single pin i made was appearing in the beauty category and everybody could see them, then on the 3rd day of doing this, i noticed that no matter how many pics i pin, only one of them was appearing in the category page.. and today i posted like 20 more pics and only 1 or 2 appeared in the category page and now no matter to which category i try to pin, my pic does not appear in the category`s main page = less repins.
I made a new acc few mins ago, tried to pin a pic and boom, it appeared on category`s page instantly.
So either they have an automatic system which checks your pins and prevent you to spam the same category rapidly, or they do manual reviews and block your pins to appear on the category.
Actually i can pin and my followers can see them, but they are not going to main page of categories, in this case i really wonder what is going on.
If it is a temporary thing, then no probs, but if it is permanent then it sucks.
if someone finds an exact answer about this problem, please share! i want to know what is going on...