VPN interface is up.

Confirmed by many steps as shown below.

NAT setup to use the VPN Gateway.

Firewall rule setup to route a specific Client through the VPN Gateway.

Problem is that

Check the Interface on the Dashboard.

It has an IP and is connected.

On Dashboard, VPN graph shows mostly static up and down data.

Navigate to Status → OpenVPN, shows the VPN is up.

Navigate to Status → Gateways.

Shows the OpenVPN Gateway is Online.

Navigate to Diagnostics → Routes.

As can be seen, only the Monitor IP setup against OpenVPN is showing as connected to ExpressVPN Gateway.

Navigate to Firewall → NAT → Outbound.

A copy of the automatically created rule, LAN to WAN, and simply changing Interface to the VPN one.