Regarding the issue your having is the RUT device that will be acting as a server is having a Public IP address? A copy of the troubleshoot file will be a great help. I will be needing the two copies of troubleshoot file from those routers of yours you can send it to me via private message.
Also before download the troubleshoot file i suggest to reapply the configuration of your OpenVPN config and let the device to be turned on for 5-10mins (Don't reboot or cut the power of the device after the re-configuration is done.)
Waiting for your troubleshoot file.