Although your device may be SIP enabled, all features and functions may not work Skype Connect/SIP.
With our service, it is highly recommended that Skype Connect certified devices be used. Skype Connect certified PBXs have been thoroughly tested with Skype Connect and its features, and provide the best results. In addition, PBX vendors that offer Skype Connect certified PBXs provide user guides on how to configure and set up Skype Connect with their hardware.
Below is a link that will provide more detailed information:
Please let us know if you have further questions.
Skype Enterprise Support