Model and Router not connecting cm400 and R6080

Just moved into a new apartment. Misheard the lady and I bought just a router, and it ended up being that I needed both a router and a modem. Went back and bought a modem to go with the router. They're both Netgear products. I was told they would work together even if I didn't purchase them as a set. Now I can't get them to connect. The modem works fine, if I plug it directly into my laptop there aren't issues. When it's connected to the router, however, through ethernet cable they cannot connect. Please help...?