Solution
To locate the problem, enable debugging and execute the display command on the DHCP relay agent to view the debugging information and interface state information.
Check that:
DHCP is enabled on the DHCP server and relay agent.
The DHCP server has an address pool on the same subnet as the DHCP clients.
The DHCP server and DHCP relay agent can reach each other.
The DHCP server address specified on the DHCP relay interface connected to the DHCP clients is correct.