Thank you for reaching out!
It would be great if you could share you OpenVPN configurations on the client and the server side.
For the RUT240 client, a troubleshoot file can be generated which will contain all the needed configuration and some logs for troubleshooting. This file can be generated by navigating to System → Administration → Troubleshoot and attached to the original post along with server config file. These files will only be visible to Teltonika moderators.
Is the issue only with the RUT240? Or did you get this setup working as a client on other devices?
Also, make sure the push options on the server side contains all of the necessary information like subnet and the netmask.