Microcom 424M Operator's Manual page 196

Chapter 11
During download the status indicator light flashes red in color:
 The file contains an illegal operation / command.
 The graphic or font is not valid or has errors.
 The intended memory slot is already occupied.
 Verify that the printer is properly configured for the type of download being sent.
 Clear memory and attempt download again.
 Verify that the format has been created properly.
324M/424M Operator's Manual - 880026-0144
Troubleshooting
11-3