The BToE (Better Together over Ethernet) needs to be enabled on the Skype for Business server. Please ask your network administrator to enable this feature.
The following steps show how to enable BToE on the server:
Use the cmdlets “Get-CsIPPhonePolicy” to review the BToE status.
If the value of the “EnableBetterTogetherOverEthernet” is False, use the cmdlets “Set-CsIPPhonePolicy -EnableBetterTogetherOverEthernet $True” to turn it to true. Then the BToE feature will always be enabled.