Cannot sign in to a desk phone using Teams SIP Gateway

Bronze Contributor

Hi all,


I'm attempting to sign in to a Polycom CCX VVX 411 desk phone I have onboarded to the Teams SIP Gateway by following the instructions here. As far as I can tell, the device has been configured correctly; it's got the Teams background image and when I press the Sign In button, it displays the sign in URL and pair code.


When I visit the URL, enter the pair code, and sign in with my credentials, the web page says that I have successfully signed in. However, nothing happens on the phone. I've made multiple attempts from a couple different phones over the past few days.


I've got a ticket open with Microsoft 365 Support, which is going about as well as you would expect. Is it just me, or are others having this issue as well?


Edit: I mixed up the model name.

14 Replies
Hello Ryan, I do not see the CCX 411 in the compatible phones list
Did you successfully use a CCX against SIP Gateway in the past?
Hi Andres, thanks for replying. I mixed up the model name; I meant VVX 411, not CCX.

Am I getting no replies because it's working fine for everyone else, or is nobody else using this feature? :)

best response confirmed by Ryan Steele (Bronze Contributor)
I finally got connected with a helpful Microsoft 365 support rep and it turns out the problem was that the "SIP devices can be used for calls" setting was not enabled on the Calling policy assigned to the user.

My fault, to be sure; that being said, it would be helpful if there were some kind of error message during the web sign in process if the setting is disabled rather than being told "You have successfully signed in". May my misfortune serve as a warning to others.
Hello Ryan,
Great news then...
That step is indeed in the procedure

I agree that a meaningful error message would be better

@Ryan Steele 


I bumped into this issue too recently. It was working months ago but unfortunately not now.

I've confirmed the SIP Calling was enabled on the call policy. So we may need to drill down further with Microsoft Support.

I've been through that common issues doc, checked every setting I can think of on a Yealink T46S, but getting a similar issue. Sign-In screen is up, sign-in on web shows success, but the device never updates and remains offline in the Teams AC.

I am seeing network traffic on the designated ip/ports for a certified teams phone plugged in right next to this SIP phone, but no inbound traffic coming from the SIP gateway to the Yealink. I'm wondering if there is currently an issue with the provisioning service?

I have found a solution to this issue that seems to work. I'm using Poly VVX 410/411 phones as Common Area Phones via the SIP gateway.


I found that with some newly-created CAP user accounts, I would log into the account using but the phone doesn't do anything except to continue to display the code. Eventually the code display times out and the phone returns to the login screen.


I discovered that the CAP user account didn't have a phone number assigned, even though I had set the number using PowerShell. I assume I had tried setting the phone number too soon after creating the user account and background processing hadn't completed yet. I re-assigned the phone number using the Teams Admin center under Manager users and the phone now completes the login and provisions itself in Teams as expected.


Good Catch Essam.
I'm able to sign in now too and my issue was due to Intune & MFA Authentication blocker. As soon as bypassing them and it is working fine again.

@Andy_Chau Having MFA authentication enabled won't prevent a user from signing in to the Teams SIP Gateway. However, if you have a Conditional Access policy configured that restricts the locations a user can sign in from, you do need to make sure the SIP Gateway IP addresses are allowed, as documented here.

We are still experiencing this issue in approximately 1 out of 10 phones in organization. We are using poly lens as our provisioning server. We have confirmed that it not a user account problem, as the same account works on another phone.
We made DHCP reservations for the Phones in question, and point the provisioning server directly to Microsoft, it works.

@Olusteve There is a known issue which affects devices that were enrolled in Poly Lens while they were signed in to the 3PIP server. When the factory reset is initiated, the phone backs up its local configuration to Lens, and these settings get written back to the device after the reset completes. This breaks the SIP gateway configuration. Could this be impacting you?


The workaround is to delete the device from Lens, then re-enroll the factory reset device. More info in my comment on this blog post: Upgrade Skype for Business Online (3PIP) phones to Microsoft Teams using SIP Gateway - Microsoft Com...

I had a similar issue but did have the correct calling plan set. For me the issue was that the phone BIOS was not at the required level. Since the BIOS was a later level than shown in the update instructions for the phone I had to guess at the exact level. After a few tries it updated.