You have probably not been able to validate your account by email. DriversCloud is currently experiencing a service interruption on its emails for about two days. It seems to be a configuration problem with OVH. I'll try to fix it quickly for this weekend.
Sorry for this unwanted outage :(
Edit: The problem is solved. If you have created an account, I invite you to validate your account in the red box that appears on the site. You will receive a validation email again.