On April 5th 2016 Sortd for Gmail version 0.21.2 has been released. This sees a major upgrade to the backend for stability, but no new features, please see the Release Notes for details.
If you run into problems please ensure you have the latest Chrome Extension, and then reload your browser tab once you have the latest version.
If you run into problems with upgrading the Chrome Extension, please uninstall the extension and re-install it. You may have to log out of Gmail and then back into Sortd again, but you won't lose any data.