FortiAuthenticator user disable before approve process

Hello, 

 I have a problem with disabling usernames that register on the Captive Portal create on my FortiAuthenticator.
After the registration but before approval by an Administrator, if the user tries to authenticate with the credentials they registered with, the FortiAuth disables the user and the link that comes (with email) to Administrator or sponsor generates an error and cannot be approved.
I have to go into management and reenable the user manualy.
Any ideas to avoid this?

Thank's