Network setup

I just switched from ATT Uverson to Xfinity.  I had the Uverse router connected to the Netgear AC1750 and was using the AC1750 as and access point.

So I bought the Netgear CM 1000 to connect to the internet and then changed the ac1750 back to a router.

I have not been able to get this to work.  Do I need an Router and not the CM 1000 modem to make this work and continue to use the AC1750 as an access point?

On top of this I also have a netgear gigabit switch to connect all my Ethernet devices.