Connexion fail : error message

[cemcha]

After installing this plugin in our Mantis V2.9.0, in the begining, when i click on the buton : nothing happened like the button is inactif.

My collegue help me and put in comments this part in the file "plugin.js" in folder assets>js to active the button :

 /*/frm.children('#sign_with_google').on('click', function(){
        return false;
    });*/

So, I can clic on the buton and sign with Google (but it's normal to must put in comments some code ?). But just after when normaly I should be redirected towards to my Mantis I have several error message
![plugingoogleoauth_curl error 60 ssl certificate problem]
: SYSTEM NOTICE : 'Use of undefined constant plugin_GoogleOauth..." (cf screenshoot)

Now, i can to connect in Mantis with this plugin but i must change connection information in php.ini

Thanks in advance for you help ! :)