Modem CM600 connected to WNDR4500

I just replaced my old surfboard with the new Netgear CM600.  I have a Netgear WNDR4500 router.  The router does not recoginze the modem.  After I connected the two I have a huge drop in Mbps; 33/34 and ever lower.  I should have at least 100 to 200.  I directly connected the modem to computer and it doubled.    Does anyone have any adivice on how I can sync the the modem and the router and increase Mbps to a least 100.  (BTW the ISP service came out to my house to try and find out why our speed is so slow.  Its supposed to be at least 200 Mbps up to 500.  The ISP service claims that its an amplifier somewhere out in the neighborhood........to be fixed later.

Thanks