NetGear WiFi Range Extender AC1200 Model EX6120

I have a Windows 10 Thinkpad laptop and an iPhone connected to the EX6120 in Extender Mode. Both devices work perfectly with the Extender.

I introduced another Windows 10 Thinkpad laptop but get the message "Windows has detected an IP address conflict". Both the Windows machines are configured to Obtain an IP address and DNS server address automatically. But, no luck with the new laptop.

Have also tried static IP and DNS but still no luck.

Have diagnosed both the wifi and ethernet hardware and software of both machines and everything is working. Also, completed the usual ipconfig/release/renew/et al instructions but no luck.

Any ideas?