In case of inteno gateways, they automatically generate the credentials, and the platform creates a "sticky" association with the gateway. If the gateway previoulsy has ben associated with the platform, the credentials need to be reset. Note that this is what the "Reset password" button do under the Edge Client settings - not "Create New credentials".
Generally, gateways fetch the edge-apps and configurations from the back-end and after a reset, it should automatically re-install apps and re-configure the settings from back-end. The server it connects to is persistent.
However, the zwave network layout is not retained, and devices need to be re-included in order for them to sync up with back-end.
To fix your gateway, it should be enough to
1) remove /etc/iot-open/iotopen.json
2) press the "Reset password" button in the platform
3) re-run /etc/init.d/register-gw start (edged and scheduler might also need a restart to update configuration)
one can also just remove the iotopen.json file and reboot the gateway to get a clean start. ( make sure to press the reset password button before it comes back up again)
