Lexmark CS963
Try one or more of the following:
From the control panel, navigate to Settings > Reports > Network > Network Setup Page.
Check the network status on the printed page.
If the problem persists, then go to https://www.etherfax.net/lexmark.
Is the printer unable to detect the internal option that you installed? Check the following information to resolve the issue.
Configure your printer and computer so they can communicate after installing a serial port on your printer.