Poly Trio and VVX phones at one site are unable to sign-in to Skype for Business Online
Customer reported that almost all Trio and VVX phones at one site were unable to sign in to Skype for Business Online (O365). There were some phones that would intermittently sign-in but would get signed out after few hours at this site.
This issue was caused because some of the necessary IPs and ports required to be able to connect with O365 were blocked at this site. The logs showed that when the phone failed to sign in, it always tried the 20.190.x.x IP address range in O365 whereas when it did connect successfully, it tried the 40.126.x.x IP address range. Both these IP address ranges are required as specified by Microsoft in the link below: https://docs.microsoft.com/en-us/microsoft-365/enterprise/urls-and-ip-address-ranges?redirectSourcePath=%252fen-us%252farticle%252fOffice-365-URLs-and-IP-address-ranges-8548a211-3fe7-47cb-abb1-355ea5aa88a2&view=o365-worldwide#bkmk_lyo After the necessary IPs and ports were unblocked all phones signed in to Skype for Business Online successfully.