I have an UC520 with a couple of 521 IP Phones. I configure the UC520, plug the phones to the integrated switch and they don't want to register. The display keeps showing "Registering"... "Initializing Network"... "Downloading SEP<mac>.cnf.xml" ... "XMLDefault524G.cnf.xml".
When I want to configure the type of phone, I don't see anything like CP521.
Do you know which type may I use or the firmware I need to register successful?