Fresh Easydiscuss 4.0.5 installation failed in back-end

Dear Team,

I made a fresh installation of Easydiscuss 4.0.5 in a fresh joomla installation (3.5.1, PHP 5.6.X) and I get the following error: "HTTP ERROR 500" in back-end. In front-end, Easydiscuss works.

Easydiscuss installation process without any error,

At the end, I have got the choice to see the back-end or the front-end.

When I choose front-end, easydiscuss works perfectly but if I choose see the back-end, it's not possible to see the back-end. I got this error :

"La page localhost ne fonctionne pas

Impossible de traiter cette demande via localhost à l'heure actuelle.
HTTP ERROR 500"

"The localhost page does not work

Impossible to handle this request with localhost at this time.
HTTP ERROR 500"

In back-end I have got the easydiscuss menu in the components' menu but each link in easydiscuss menu gave me this error too.

I don't have any trouble with virtuemart installation, easyblog installation, jomsocial4.2 installation, kommento installation, ...

Thank you so much in advance for your answer.

Best regards,

Tony