The Microsoft Authenticode signature of the package downloaded from the Package Library failed to be verified.
The most common cause of this issue is that the root certificates Windows uses to verify Authenticode signatures have been corrupt or missing. See this Microsoft Knowledge Base article for more information. It could also be caused by the file being altered or corrupted during download. The error message will contain some additional information about the exact nature of the issue.
Ensure that the root certificates are installed and that there isn't something corrupting the downloaded package and try the download again.