Question : HELP! DHCP not assigning IP addresses

Hi,
This morning people can not log into the network, I have checked the DHCP and it's not assigning IP addresess, I have got people back onto the network by going round and manually putting IP addresses in which is ok for now but how can I get the DHCP to start giving them out again, when users try and log in they get a DHCP can not be reached message, I can ping it fine and all looks ok.

Answer : HELP! DHCP not assigning IP addresses

are there IPs available in the pool?
did you restart DHCP server service?
Is DHCP server listening on interface you use for communication?