Why can’t I download VR content that I purchased on Viveport?
Please note that it's not Viveport but the VR content developer or publisher that decides which Windows environment is compatible with the VR content. Before making the purchase, it's important that you're aware of your Windows environment.
If you're not otherwise experiencing a compatibility issue, there's a chance that your purchase wasn’t updated correctly due to poor network connection. Try to sign out and sign back in to your HTC Account. On the Library tab, select the VR content, and then click Install.