only one divice is recognized on the ethernet switch

We do not have wifi. We have the modem connected to the switch. The PC is connected to the internet through the switch, but the laptop is not finding a valid IP address. I have checked the cables and they all work correctly. The laptop works if connected directly to the modem. And the PC will work in the Switch if the laptop is connected or not. THe laptop will not work with the switch though. What is up?