One work around is to set a static IP for the new devices and force them to be within your range

It's somewhat like a static IP address, but without the hassle of all the extra configuration steps

j. Much more, including static ip reservations, wake-on-LAN, port forwarding, etc

You can do this by setting your dynamic IP address range like this

Static IP: Ax11000 allows single toggle button to each of its connected devices to get Static IP, which is based on MAC address of the device and handled by router side, so even after reboot of the router, this feature remains

This allows you to set the VPN up without a static IP or paying for a separate DDNS service.

For example, the UI makes it easy to set static IP according to MAC addresses

Also, setting static IPs or IP conflicts problems are commonly frozen your network