To resolve:
- Use the fax cable that is included with your all-in-one printer.
- Insert one end into the LINE IN or EXT OUT port.
- If you experience difficulty inserting the fax cable, use a known "working" telephone cable (RJ-11).
- Use the telephone cable that is connected to your telephone.
- Re-insert the telephone cable into the LINE IN or EXT OUT port of the printer.
- Connect the other end of the telephone cable to the wall jack, or DSL filter, or ATA depending upon your phone service.
- Inspect the LINE IN and EXT OUT ports for damage.