After transfer, for security, http downloaded files may be 'blocked'".
Then you have to unblock them one by one. In Microsoft Windows, you must:
oSelect the icon of a concerned file.
oRight-click to display its context menu
oAnd click on the 'Properties' command
oSelect the 'General' pane
oCheck the box 'Unblock', bottom right (if it exists).
oClick on 'Apply' and then on 'OK' to exit the menu.
Under the other systems, it's 'mutatis mutandis' pretty much the same procedure.
Warning : Under the latest versions of windows, it is also possible that the installation is prohibited with a mention 'Unknown Editor', for example. You will need to override warnings and allow installation.
On Windows 7, 8 and 10, you can have messages like:
Windows protected your computer
It will be necessary to click on: 'Additional information' to be able to install the program!Enter topic text 'here'.