This error message may have various causes:
Check if the device file is specified correctly in the Configure Dialog.
Make sure that your kernel supports the serial ports.
See that you have read and write permission for the device file. Some facsimile systems (e.g., HylaFAX™) reset those permissions.
The device file may be used exclusively by another process. In this case terminate this process.
The DSR signal could not be detected on the serial device. This means the modem is turned off or it is not connected to the serial device specified in the Configure Dialog.
The CTS signal could not be detected on the serial device. This can be observed when the modem is receiving a facsimile or is answering a phone call. Your telephone may also be off hook.
The modem did not respond to a command. Try to lower the device speed in the Configure Dialog.