Thank you for your support,below update from my side.
RUTX08 has Internet access from the WAN link. This access is filtered and blocked by the ISP (connected to the WAN), we have the 940 router for remote access. Only the 940 i can add to the VPN HUB because i have the internet via the 3G SIM.
The thing is that the device under the X08 has the default gateway from the ISP. When i want to connect from the HQ, via openvpn to the 940 ...and then to the device under X08, this device does not know how to return the traffic to the HQ PC due to the default route...that sends the traffic to the WAN ISP.
RMS - i added all the routers to RMS but for sure the X08 will not be accessible due to the filtering. The RUTX08 is like a backdoor.
I will try with a static route on the X08 to connect on the Virtual IP that the Open VPN will provide to the RUT940...this is the test that i want to try.