I bought a CISCO CP 8861 phone from an online retailer since it was on the list of phones supported by RingCentral. I tried to auto provision and it failed. I then tried to reach the phone using its ip address in a browser so that I could manually provision. I kept getting a message that the connection was refused. I could ping the phone but not get it in a browser. I spent an hour with Ring Central tech support and got no where. Then it was another hour with CISCO to learn that I needed the support contract number held by the Amazon seller. I called him and found out the answer to the problem, which I am posting here so other users don't waste 3 hours. When you buy a CISCO phone from Ring Central it is a 3PCC model and will work. When buying from others, unless your get the 3PCC model, the phone will never work on RingCentral. Why? CISCO originally built its phones for CISCO phone systems. The normal phones, no matter what model number, such as CP-8861 or what ever, were only designed to work in the CISCO environment. CISCO then noticed that people were signing up with RingCentral and buying competing phones. They developed versions of their phones that have the 3PCC number after the model number to work in other systems. So, if the phone does not have a 3PCC number do not buy it.