121.71A error code at first boot up or while printing or doing a calibration
Turn the printer Off and turn it back On after a minute.
Check the printer if the error message still appears.
If the issue does appear, please contact Lexmark support for further diagnosis of this issue.
An "Invalid Engine Code" Error is Appearing on a Lexmark T64x Series (T640, T642, T644) or an X64xe Series Printer
Does a 900 error message appear on your printer? Check out the following steps to troubleshoot the problem.