How do I install extensions in Fireworks CS6?

When I try to install the Fireworks CS6 extensions through Extension Manager CS6 I receive a message that the extensions do not have a valid signature, even when I launch the Extension Manager and try to make a first configuration and installation of the extensions that come with the Creative. Suite 6, gives me an error and does not install them.

Working on PC with Windows 10 Pro, which prior to the installation of Fireworks CS6 from Adobe Design and Web Premiun, has several Creative Cloud 2018 applications installed.

How can I fix the problem.

Thank you.