This can happen when the modem permissions are not set to allow faxing.
1. Go to Start -> Settings -> Printers and Faxes
2. Right-click on the Fax icon and select Properties.
3. On the “Devices” tab you should see your modem. Make sure that the modem is enabled for fax sending.
4. If not, click on properties for the modem and click “Enable device to send”
