Good morning, I'm having an odd issue with CX Programmer and have hit a wall. I'm trying to upload a previous version of a program to an existing PLC (CS1G-H CPU42) and I keep getting the following error when I compile while online: "The read protection properties which are not supported by the connecting target PLC are set. Check the unit version of the PLC." This prevents the program from being uploaded. I have a first revision CS1, manufacture in 2005 from what I can tell. This exact program has been uploaded previously, but a modified version replaced it recently and I need to go back to the older version. Things I have tried so far. without success: - Removed UM Protection - Made sure Task protection is off for all tasks - Check DIP Switch #1, which is write protection, and made sure it is off - Used "Remove Password" and "Release access" functions from the PLC/Protection menu - Used the auto-verification to confirm the configured PLC is correct - Reuploaded a full backup of H & D memory, from the older program I am able to compile the program when offline, but it chokes when online. I am connecting to the PLC via a serial cable. I haven't found any help from the CX Programmer help, or the CS1 programming and operation manual. This error message is nowhere to be found. Anyone has a clue ? I'm at a loss right now. Thank you !