Hi there,
You probably have the DHCP console installed on your Domain Controller but are running the DHCP server on a different server. Run ipconfig /all from a DHCP client and see what it lists for a DHCP Server.
And also you only need to add a new dhcp scope if you have added a new network segment that is using that IP range.
You cannot just add the scope and have it shared with another on the same network segment
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