[Observium] Device not visible

Hello!

We have a device that is no longer visible in Observium. It is not in the device list and the search function can't find it. I tried to add it again to Observium, but get this message: "Already got device xyz."

Running "./discovery.php -h xyz" returns this: "WARNING: 0 devices discovered. Did you specify a device that does not exist?"

Is there something wrong with our database? How to fix it?

Thanks, Siegfried