Open the Event Viewer applet on your Essentials server, go to Windows Logs → Application, and take a look in there for any error events that give an indication as to why your license is invalid. You should see an event getting logged that shows two hardware strings not being equal (≠), which results in the license being considered invalid. If you provide that information to me, I can tell you exactly what is causing the issue. Otherwise, there should be one or more events getting logged there that provide error information if a licensing error is getting thrown, etc.

That being said… Have you made any hardware changes to your server (or to the virtual machine’s configuration if you happen to be using a VM) since you first ran the WSEE Installer? Changing the server’s underlying hardware configuration will indeed cause the license to become invalid. To resolve the issue, you will need to run the WSEE Updater on your Essentials server. Doing that will (re)link your license back up to the server once again. You can download the latest release of the WSEE Updater from here. If the WSEE Updater happens to inform you that the latest update is already installed on your server, then simply check the checkbox stating that you would like to reinstall the update anyway.

Thanks for getting back to me. I am wondering if the licence message was a red herring. Looking through the logs, I can’t see anything in relation to hardware strings, errors, warning nor information entries. I am running on the physical hardware now, where the only thing which will change will number of drives connected.

At around the time of the issues, I saw the backup service crashing in the logs, then from then it seemed there were a few other .Net applications crashing, which included the WSE dashboard, and services until I rebooted. I am going though the WER logs to see if I can find what the cause was. I think bottom line is the problems with the WSEE was a symptom of something else failing. It may even be a quirk of an OS in its infancy.