FortiWiFi 60CX-ADSL-A issue to setting up ADSL PPoE from ISP FAILED always

Hello everyone,

My device is a Fortinet FortiWiFi 60CX-ADSL-A (Firmware version v5.2.9,build736(GA))

I have login and password from our ISP where these informations are set into the LIVEBOX ADSL and the LiveBox works fine with them.

The FortiWiFi 60CX-ADSL-A can use PPoA or PPoE and i found that i have to use the PPoE... But, when i try to set username/password the interface status says "failed"

in the CLI we can see CHAP Error : 

On the GUI  : 

Other information about the status Led on the front of the device :

ADSL sync : Fix

ADSL TX/RX : Blink

If someone has already seting up a device like this with ADSL please help me because i lost more 2 weeks on it and never find the solution and the Fortinet support says this is a problem with your ISP but as you see above in my post, the login and password are correct.

The same issue with a Fortigate 30D.

Regards,