Due to the long validity of (old) gateway access tokens, we can’t release gateway IDs to be registered by different users. If you still had access to your old account you could have transferred the ownership of the gateway to your other account, but if your old account is deleted, that will not work.
You could register your gateway under a different EUI, or you could register a human-readable GatewayID and use an MQTT forwarder to connect to TTN.