I also bought Pigments 3 bundled with the 5 spectrum packs. I installed it perfectly from the Arturia Software Center, and as for the packs, 4 of them installed fine from the Store view within Pigments, but one of them (Crimson) showed as downloaded (blue check mark) but not in "My Banks" like the others. Following advice on this thread I went directly to the website in My Products, clicked on the Crimson download link (the word, not the down arrow, which was broken,) closed Pigments, ran the installer, and when I opened it there it was in My Banks
If you are still having problems I encourage you to contact support.