Zebra S400 does not keep the calibration settings. After calibrating or restoring factory settings (like described in the manual) first label prints OK (using BarTender software) then it's off again. Same happens if turn printer off and on again. Is there any internal battery what keeps (manual) calibration settings?

It appears to be a well documented issue. Try the Zebra Support Forum.

https://www.google.com/search?q=zebra+gx430T+wont+calibrate

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I think this is more related to the calibration of the label each time you change the new label size. I use ZM400 and your printer should also have the same setting. Under setting, put the When Head Close setting to Calibration. This will let the calibration perform automatically when ever you load a new label size and close the print head. Well 2 label will be lost every time.

load the paper and the Ribbon CORRECLY, check if the ribbon is not on top of the label sensors and gap sensors.
run manual calibration, press the last button until flash 3 times (to save), turn printer off, and on again.
If presist, download the correct driver (www.seagullscientific.com) run Reset to Factory Defult) from this driver.

You have to program the tearoff.
See the manual or use a windows driver to end the value to your printer

i think it's a GAP problem, try to calibrate from the computer, if that's not solve the problem, find the CALIBRATE option on the LCD panel a. just follow the instruction to do manual calibrate

Remove the ribbon. Load the direct thermal stock. Power the printer down. Count to five. Return power to the machine and then press the calibrate button (go throught the calibrate sequence). If that does not work. Let me know. There is a way to return to factory defaults and it should sense when you have a ribbon loaded and go to direct mode automatically.

Reset it to factory default.

Have you tried cleaning the sensor? It is underneath the labels oppoistethe print head.

The factory default settings for the S600 is to auto calibrate every time the printhead is closed and every time the power is cycled. If the media sensor is not positioned correctly for the media you are using the label size will not be detected during a calibration. You mentioned the media has no markings, doe sthe media have a space between the labels? If so, the media sensor may not see the gap in the labels adn therefor is not calibrating properly or not calibrating at all. Check the media sensor position. I have found that the media sensor must be at least 1" from the inner wall of the printer so it doesn't see the edge of the backing in oder to read the size of the labels.

I had this happen when I changed from one label to a different size label. It needs to be calibrated. There are several types of calibration to do to the S600. Here is the solution that worked for me.

1. Check the position of the laser Media Sensor (figure 13). It may need to be moved to match the type of label that will be printed.

For CARD labels, the media sensor needs to be set at the edge of the card so it can “see through” the notch that is cut on the edge where the perforation is.

1. For STICKY labels, it can “see through” the backing which shows between each sticky label, so the Media Sensor could be set anywhere for it to work, but will probably be set towards the middle.

Set to Factory Defaults. This is so that all of the following steps will work. I do not need to change the steps based on the type of mode that printer is set up in because it will erase all that by setting it to the factory default. (See figure 14 for buttons)

1. Turn off the printer.
2. Hold the FEED and PAUSE buttons down as the printer power is turned on.
3. Press MODE button four times.
4. When the defaults are saved to the printer, the CALIBRATE, DARKER, and POSITION lights will all flash.

Test to see if the calibration is set correctly for the label. If not, proceed to the following steps.

1. Do a Manual Calibration.

Turn off the printer.

1. Hold the PAUSE, FEED, and CANCEL buttons down as the printer power is turned on, keeping the buttons depressed.
2. This will run through several labels and do some printing.
3. Release all three buttons after the CALIBRATION light comes on and then goes back off.

Put the printer into Auto-Calibration Mode.

1. Turn off the printer.
2. Hold PAUSE, CANCEL, and MODE down as the printer power is turned on.
3. Release the buttons after printer is powered on.