With so little information it's difficult to judge what the problem is. Make sure your operating system, whatever it is, is totally up to date, including your IE browser, even if you don't use it.
If you had security software installed previously it's recommended you remove it and use any removal tool available.
If the download isn't working from your online account try another browser.
Lastly technical Support is available 24/7 free by phone or online chat and linked under Useful Links at the top of this page.