Unable to download iMovie

I accidentally deleted the app and am now trying to re-download the app. However, when I try to download a message error appears saying "iMovie failed to download: Use the Purchases page to try again." I thought I might not have the right version of software but it says it needs 10.10.02 or later as I have 10.10.03 software version. How can I fix this so I'm able to download it on my Macbook Pro?