I currently use a card PLC P342020. I am able to connect to it but when I try to upload my program to the PLC, I recieve this error message: Failed to check compatibility.
Can anyone help me?
Most likely the CPU and/or FW reference do not match what is actually there:
Ensure the correct CPU model number is selected and the correct firmware is loaded. I think you might be able to select a lower FW rev in Unity than is actually on the controller, but not the other way around.
Another thing to do is start a new project with no configuration and extract the current running one (if one exists), and then you will have valid model number and FW rev to use.