Thanks to some user reports this morning, we found and fixed an issue with Koken that would make it appear as though you were still logged in, even though your session had expired. This would cause confusion as any actions (uploading images, creating new albums, etc) would fail because the session was no longer authenticated. We've just released 0.5.5 to resolve this issue.
To update your installation to 0.5.5, sign-in to your Koken installation. Underneath the main navigation will be a message row asking if you'd like to ignore or install the latest version (see screenshot below). Click "Install now" and your installation will be automatically upgraded to the latest and greatest. If you have issues with the upgrade, try signing out first by clicking your name in the upper right corner of the screen, then log back in and try the upgrade again.