Unable to download purchased songs to library

My sister bought an album on iTunes on her computer (same as mine) and the songs downloaded into her library, but when I tried to download them on my computer, the songs just have 'Purchased' next to them and I can't download them. My phone has the same problem. My sister and I share the same account and my computer is authorised, but I don't know why I can't download the songs. They don't appear in purchased songs on iTunes, but when I search it, it says they are purchased. I normally don't have a problem with downloading purchased songs, and I even downloaded a song that I bought the same day without a problem.