DHCP problem?

I have XFINITY modem in Bridge mode. Connected to an Asus wireless router. I have several devices cabled to router and WiFi was working fine. When I disconnect my Mac laptop which has wired connection, the router loses internet connectivity (error message between ISP and router and all WiFi connections lost. When laptop plugged back in, internet connectivity restored and WiFi connections begin to work again. I’m guessing this is a DHCP problem but am clueless how to fix. Help?