5.1 sound set failed to download

I downloaded the 5.1 sound set from the PMDG Op center, but halfway through the download it got stuck at 0kb speed, I tried cancelling, and nothing happened, it just said "cancelling". I then closed the Op Center, and started it up again, but now 5.1 is available for me to select, even though it didn't download the files correctly. How do I reset it so it downloads everything again? Thank you, David Lee