Problems when registering FortiClient to the EMS.

Hello guys I am having troubles while trying to register one wokstation, it won't allow me to register the client, I am getting the following error:

EMS Internal error.

It is important to mention, this workstation is set up under a different domain controller, the computer does not belong to our domain because this is an specific case where a user out of the company need to connect to our systems. Do you think that could be the issue?, pls let me know if any other information is required.

Hope you can give me a hand, it will be much appreciated.

Thanks!!