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Your forwarding rule does look to be configured correctly.
Could you also attach a screenshot of the Network -> Interfaces -> General page?
Attaching requested screenshot
It appears that 172.23.40.178 is a private IP, not routable over a public internet.
This means that you are either:
If the later is true, the, as an alternative, you can check the ZeroTier VPN configuration example in a link below. This might help you solve your problem as this VPN solution does not require you to have a public IP, simply access to the internet: https://wiki.teltonika-networks.com/view/ZeroTier_Configuration.
Alternatively, please check Teltonika's Remote Management System, specifically RMS Connect or RMS VPN HUB features, which allow you to access devices connected to Teltonika routers and gateways without the need of public IP: