What type of phone line are you using?
Dedicated line: A standard analog fax/phone line assigned to receive or send faxes.
The phone line should be for product fax use only and not shared with other types of
telephone devices. Examples include alarm systems that use the phone line for notifications to a
PBX system: A business-environment phone system. Standard home phones and the fax
accessory use an analog phone signal. Some PBX systems are digital and might not be compatible
with the fax accessory. You need to have access to a standard analog phone connection to be
able to send and receive faxes.
Roll-over lines: A phone system feature where a new call "rolls over" to the next available line
when the first incoming line is busy. Try attaching the product to the first incoming phone line. The
fax accessory answers the phone after it rings the number of times set in the rings-to-answer
Roll-over lines can cause problems with receiving faxes. Using roll-over lines with this
product is not recommended.