RingCentral Polycom not working. DHCP Failed message.

Does the modem provide DHCP?  Sounds like no IP address is getting assigned.  What happens if you plug the phone directly into the modem?  Note that most Polycom phones have a 2-port switch built in, so you could go from modem to phone, then from phone to PC or second device.

I'm not sure on the DHCP? Technically the phone is plugged directly into the modem via  the switch, correct? A switch doesn't have a separate IP right? Right now I got cable modem>switch>polycom phone (reason being is I have 3 other devices running thru the switch and the modem only has one outbound ethernet line. 

Depends on the switch setup but typically, yes.  The point is, something needs to assign an IP address to the phone and it's requesting it but not getting an address back.  Either the modem is not configured for that or the switch is not passing the request (or the response) along.

Ok, so the modem is a netgear CM1000 and my computer hooked up fine and so it would appear that it is assigning an IP address to at least that. How can I go in and assign an IP to my phone or how would I know if my modem is configured for that?

I'm not really sure.  I would contact RingCentral support for help with troubleshooting the phone configuration.

A lot of modems are modem/router combinations. The modem brings the service in, the router handles all communication on the network and hands out the IP addresses. Your modem doesn't have the router function built-in, and will not handle IP addresses or your network traffic. Some computers are designed to work with this type of connection, which is why it may have been working for you. You will need a new router, or a modem/router combo.