Hello,
Could you try to remove remote network IP address and remote network subnet mask values from client's configuration?
These values are pushed by the server anyway, yet the device indicates failing to add this route, which might be due to this redundancy in the configuration.
There is also a warning to keep in mind, though replacing this option may not help:
- WARNING: --ns-cert-type is DEPRECATED. Use --remote-cert-tls instead
Another suggestion would be to update your device's firmware. If you have important configurations, and may want to revert, make a backup first.
Latest device firmware can be downloaded from here. When updating, set Keep settings option to off. Be aware, that due to the difference between versions, you may not be allowed to update via WebUI, thus follow update via bootloader menu. For instructions refer here.
Best regards,