[Comfy.n]

Originally Posted by fredtgreco

I have tried everything to get the latest version of Calibre to install. I get the dreaded "This installation package could not be opened" error.

found this on the web

2. Check if the Setup File is Blocked

Windows sometimes applies blocks to ‘suspicious’ files downloaded. If your setup file is blocked, you’ll see an Unblock option within its properties window. You can unblock a setup file like this:

Simultaneously press the Win + X keyboard keys and select File Explorer.
Go to the folder you’ve downloaded an affected software setup file to.
Right-click the affected software setup file and select Properties.
Click the Unblock box on the General tab if you can see one.