ReSharper Installer does not run (ReSharper 4.x - 8.x)

Example error messages:

This installation package could not be opened. Contact the application vendor to verify that this is a valid Windows Installer package.

Running this package is prevented by Windows Security Policy. Please contact your System Administrator.

Possible Reason: ReSharper MSI Installer might be corrupted or blocked by Windows Security Policy.

Sympthoms:

• ReSharper MSI Installer does not have a valid digital signature. A missing or damaged digital signature indicates that the file has been corrupted during download, or tampered with.
  • Open shell properties window of the MSI file (right-click on the file and choose "Properties" from the context menu), "Digital Signatures" tab: the file should be digitally signed byJetBrains s.r.o.
  • "Details" button: there should be a label reading "This digital signature is OK":

• As a downloaded file, MSI would usually have the Internet Zone Identifier. Security policies might be configured to prevent installation of such packages.
  • Open shell properties window of the MSI file (right-click on the file and choose "Properties" from the context menu).
  • "General" tab: use the "Unblock" button to remove the Internet Zone Identifier:

Solution:

• If the file has no valid Digital Signature, please download ReSharper MSI Installer again. You might have to use a different internet browser, PC or even Internet Service Provider (ISP) to bypass the cached copy of the broken file.
• Use the "Unblock" button to remove the Internet Zone Identifier.
• Run the installer with Local Administrator privileges.