First you need to be able to recolve the web interface issue with the phone, if for no other reason than it may be needed in the future. Get the manual and do a phone reset and re-provision using the needed parameters. I have posted the a link to the blog for this model:
http://www.3cx.com/sip-phones/polycom-ip-6000.html
It might provide some insight if you can post a log. From what I gather, if a call is received by the IP6000, then all is fine in both directions. If the IP6000 is used to originate a call, then it can hear the callee, but the callee cannnot hear the caller on the ip6000.
What is the remote phone? Is it an extension of the phone system? Is it a PSTN phone? If you try from a different extension are the same results seen?