Pls open Windows Fax and Scan and check if both of the send/receive options are checked under Tools\Fax Setting\
Other check up
1. Is the modem connected directly to the USB 2.0 port on your computer?
2. Are you able to send/receive fax using a regular fax machine and the telephone line?
3. Are you able to send fax using the modem and the telephone line?