Hello,
Does your device has any additional settings, to allow remote WebUI access, like, for instance, Teltonika devices?
Does the device behind RUT have a correct gateway configured?
Do you have LAN forwarding enabled in VPN HUB routes tab next to the client device?
Otherwise, could you attach a troubleshoot file to your question. Please, replicate the issue, then access router's WebUI, go to System -> Administration -> Troubleshoot section and download troubleshoot file from there.
The logs in the file might provide more insight into the issue.
In addition, could you provide your VPN HUB name and company ID/name for further investigation?
Best regards,