Google Sign-In/Sign-Up Doesn't Work !

[Screamfox]

Hello @everyone & @Devs ,

Well i have a issue in my whmcs, i'm trying to active the Google Sign in addon but i have every-time the same issue and i verified many times the Client ID and the Client Secret but i receive everytime this error: Invalid details not saved. Please verify your details and try again.   So i have removed the slash at the end in the WHMCS System URL but after saved the Slash appear again. And i don't know if the issue come from there "Slash at the end of WHMCS System URL" , So there is how i have installed my WHMCS i have installed in the directory where cpanel at normally put the error redirect page it's in (var/www/) there is where i have installed the WHMCS and i have done a lot of workaround in the httpd.conf and other apache.config to force every http to redirect to https and to force opening the store independently or whatever you do, http --> https , ftp ---> https and etc .. 

So i have changed a lot of lines in my httpd.conf and in other apache and the problem can be from there but before sending my files (I suggest people request the exact file and say the location if dev/people need to check a specific file to get this integration sign-in working fine ) but the only thing is very weird or "bizarre" is the Facebook Sign In intergration, cuz facebook works very well, just a little problem sign-in cuz people need everytime to input info like Post Code and Phone number (IF SOME ONE HAVE A IDEA TO REMOVE THIS CUZ ATUALLY I PUT IN OPTIONAL MODE THIS THING BUT DON'T WORK) but everything in facebook sign in work fine only Google and Twitter, any idea ? if some one need a specific file ask here.

With my best regards