Trust Services Lab has been updated today:
The update does not need registration code anymore (ignore "Get Invited" link - it is leftover from previous release and will be removed). Just download SDK, visit the portal to create server, and check the documentation and samples.
Note that if you are using previous release - the current and previous services are now both alive, as completely independent services. Each is only compatible with appropriate SDK. You cannot get to the previous service using new SDK or vise versa. Please update to the new SDK/service - it offers many new features (and the old service will be disabled some time in future).