How can I register a deleted SCPF?

I built a single Channel gateway and tried to register it. I only had the gateway ID, but not the DEV EUI. It registered, but no data came in. So i deleted the gateway to register it again, but I couldn’t as I was told, that the ID is already present.
What can I do to re-register the gateway ?

Single channel gateway are not supported by TTN, please see: Single Channel Packet Forwarders (SCPF) are obsolete and not supported

You don’t. TTN does not support Single Channel Packet Forwarders as they are disruptive to the community network. Please see: