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CX500, CX600 and CX3000 log on problem to Skype for Business

Occasional Visitor

CX500, CX600 and CX3000 log on problem to Skype for Business

Hello Community,


We are having a bad time figuring out why some of our phones are not or no longer able to log on to SfB. The problem phones are a mix of cx500, cx600 and cx3000.


The problem started around the time when we migrated our Lync 2013 environment to SfB 2015 (swing migration). The phones that were at that time logged in with a user are still working now, phones that were not logged in or new devices (the cx3000) are unable to log on.


The problem phones are not contacting the server properly, not for updates, not for logons. Other phones do. Could it be that the firmware is too old now to be able to connect to the SfB?


The devices do get the DHCP options (as before), but the time when booting is off (minutes are ok, hours are wrong)


I suspect the problem to be certificate related. A wireshark trace on the SfB server shows the output in attachment (trace_on_SfB.jpg)


Another strange thing is that I don't see any traffic coming in from the phones to the CA server. One would expect the CRL check to show up?


Resetting (4+6 or *+#) the phones does not help. I've put some of the phones in the server VLAN (also with the correct DHCP options)  to rule out that possible problem.


Did someone encounter the same problem or does anyone have some pointers for me?


Thanks in advance,

Kind regards,




Polycom Employee & Community Manager

Re: CX500, CX600 and CX3000 log on problem to Skype for Business

Hello KrisV,

Polycom and other manufacturers produce these optimized for Microsoft® Lync® or Skype® for Business devices after a reference design and the embedded OS running on the phones is provided, supported and maintained by our partner Microsoft®.

You therefore may want to reach out to the Microsoft® community and / or Microsoft® support directly instead as this is the most direct and efficient path.

Polycom is unable to add any new features into the functionality of these CX Devices

Please try here

Best Regards

Steffen Baier

The title Polycom Employee & Community Manager is a community setting and does not reflect my role. I am just a simple volunteer in the community like everybody else. All posts and words are my own & do not represent the views of Employer.


Notice: This community forum is not an official Poly support resource, thus responses from Poly employees, partners, and customers alike are best-effort in attempts to share learned knowledge. If you need immediate and/or official assistance please open a service ticket through your proper support channels.
Please also ensure you always check the VoIP , Video Endpoint , Skype for Business , PSTN or RPM FAQ's
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