If your Zebra ZT230 printer is not printing and the display is showing the "Ribbon In" warning, you should set print mode to "Thermal Transfer" to clear the message and print.
The Zebra ZT230 printer display will show "Ribbon In" when the print mode is set to "Direct Thermal," as this mode does not require a ribbon.
Set your printer to "Thermal Transfer" mode to clear the warning message. Refer to page 92 of the Zebra ZT200 Series User Guide for instructions on setting print mode and page 158 for details on this warning error.
If you are unable to print after making the "Direct Thermal" setting change, power cycle your printer by turning it off and on.