My lp 2742 zebra printer won't print

SOURCE: label printer

Try reseting the auto gap detection.

http://www.fixya.com/support/p257130-zebra_lp_2844_thermal_printer/manual-19245/page-15

SOURCE: prints out 2 labels at once

I've seen this be due to dirty sensor or misconfigured media setting.  Clean the sensor in the middle of the edge on the inside and outside of the printer, then if still having trouble - Inside the printer it should tell you that if you are having printing trouble:

1. turn off the printer
2. Hold down the feed button
3. turn on the printer and at the third red flash release the feed button
4. it will then feed some pages print some info and ask you to hit feed again to exit dump
5. hit feed again and it will say exiting dump

SOURCE: Zebra LP2844 printer prints garbage

Sounds like you might be using a bad driver, or the printer is in dump mode.
Try hitting the green button and see if it says exiting dump.
If still having trouble, inside the printer it tells you that if you are having printing trouble:

1. turn off the printer
   
2. Hold down the feed button
   
3. turn on the printer and at the third red flash release the feed button
   
4. it will then feed some pagessome info and ask you to hit feed again to exit dump
   
5. hit feed again and it will say exiting dump
   

SOURCE: An extra, blank label prints from a Zebra 2746e.

Check media settings in the printer driver. Check version of printer driver. Zebra printersuse an internal printer driver with their Zebra Designer software (Zdesigner driver) or a ZUD (Zebra Universal Driver) for other windows applications. These drivers can be downloaded directly from the zebra website.

Alternatively you can download the seagull scientific driver and use that instead. (used with bartender program)

Label skipping occurs if the media dimensions are not specified correctly. The important ones are label height, and media setting for type of media.

Perform a media calibration before you go changing settings. Power on printer, Hold top and bottom buttons in on control panel for 5 seconds, release bottom button only then when printer starts feeding labels release top button. When printer finishes press feed button.

SOURCE: zebra 2488-z

Unplug the printer, place your finger on the green button and with the other hand turn the printer back on. Let the light flash four times (flash, flash flash, flash flash flash, flash flash flash flash) then immediately release the green button. The printer will cycle and feed out a couple of labels. Press the green button one more time and you are ready to go.