I can't print label from ZM400 PRINTER thru' serial port

make sure you have no network traffic for your printer and decrease the printing speed, and make sure you are using a free port not a used and default port for the service..

The printer driver settings override the printer settings unless you tell the driver to use the printer settings. You can tell by setting the printer setting and saving it permanently. Print a configuration label. Send a label to the printer. Print another configuration label. Compare the config labels and If it changed, then the driver changed it. Set the driver as above and it will not change when you print.

if you sending a file (ex. pdf or picture). to the printer, can do this, if you send the proper format with normal fonts (caracteres))to the printer, work fine. build new label from zebradesigner

You will need to build a driver for the AS400 to handle ZPL, similar to Unix drivers

Yu can rotate the print orientation in the Z Designer printer driver, in the OPTIONS tag tick the 180Deg box

send a test print from the driver.
check the connection configuration.
if connect with serial port (check seting from the port (THE SPEED HAVE TO BE THE SAME)
if connect with USB, if necessery, install the driver again and test.
if necessery flash the firmware and test (worst case scenario)
if can't comunicate and if using paralel port:
check if the fuse next to the paralel port is burn ( on the logic board.). replace it.
dont forget to unplug the power cable and the comunication cable.

In the printer setting-

Change the Print Method from - "Tharmal Transfer to Direct Thermal" and save it permanently

Two possibilities are the port configuration and the type of serial cable.

The printer has a feature that will try to match itself to the PC's configuration. Press and hold the feed button until the green status led flashes three times. While the led flashes send a ZPL format to the printer (hopefully you can do this through Design Pro by trying to adjust the printer or print labels, but the labels will not print). When the printer and PC are synchonized, the led changes to solid green.

If you can synchonize but still can't print, the problem might be the serial cable; not all serial cables will work. You should use a full null model cable (all pins connected except 1 and 8).

connect the printer to a desktop or laptop using LPT1.

if the data light comes on and nothing prints chances are that the serial settings are set improperly. all of my printers are 25 pin serial, not parallel. i don't have one in front of me but i believe the settings are 19200, 8, 1, none. hope this helps.