Your Office 365 user account is configured to use Cloud PBX.
You have an active PSTN call using the Skype for Business client on Windows, where the voice for this call uses Skype for Business Cloud Connector Edition.
You start a transfer to another phone number by selecting or entering the phone number from a list of suggested phone numbers on the transfer menu.
In this scenario, the other phone number rings, and you can answer the transferred call, but you hear no audio. Additionally, the client window of the existing active PSTN call shows the following error:
Cannot complete the transfer.
This is a known issue in Cloud Connector Edition versions that are earlier than 1.3.8. To resolve this issue, upgrade to Cloud Connector Edition version 1.3.8 or later.
For more information about how to transfer a call, see the following Microsoft website: