Check the following:

• Make sure that the tape cassette is inserted properly.
• Make sure that the tape cassette is not empty. If so, replace it with a new one.
• Make sure that the tape compartment cover is closed.
• Clean the print head of the unit with isopropyl alcohol.
• If the BIG size font is selected and any tape cassette with a width of other than a 3/4" (18 mm) is installed, "ERR" is displayed when you try to print or change the settings for SIZE, STYLE and UNDL/FRM. Turn the BIG size font off or replace with a 3/4" (18 mm) wide tape cassette.
• If the LCD displays "ERR", your text size surpasses the tape width, Refer to the related FAQ below.

If the problem persists, your machine may require service.