Can the analog phone make a call outbound or to another phone?  I'd start there.

If it can not, then your gateway is not working.

Do commands such as "show sccp"  and see if if the ports are registered with CUCM.   Check in CUCM the ports are in fact registered. 

You can also run a quick CSIM command and force a call to the analog phone. This at least tell you the gateway can make a call.  It should ring the phone.