Adding DHCP server to existing Domain

im enrolled in school taking a networking class. our lab wants us to add a 2nd server to an existing server.

server 1: has active directory, DNS, file and print server
server 2: has DHCP, DNS and active scopes

the issue is when server 2 is on the domain it doesnt assign the IP address correctly
but if its just on the workgroup it works fine. i've searched all over and cant find anything similar to my issue. does anyone have any insight?