DHCP service issue

I am using Rock Pi 3A, Ubuntu 20.04 version. After OS installation I am trying to assign the IP. Before it’s fetched default IP of DHCP. After that I changed to static Ip using NetPlan. The issue is after changing the IP, if we restart the device, again it is going back to the same DHCP ip. I don’t know what is the issue. Can you please help me with this

Ethernet or WiFi for static IP address?

Rock Pi 3A which using POE (Power Over Ethernet). It is using Ethernet IP.

You can disable this services to set static ip,

  systemctl disable network-manager

can you have a try?

Thank you, It worked.