When I try to print multiple cards, only 2 cards print, the same two all the time, the others don't
It sounds like you might have a job stuck in the print-queue. Best way to check is to start with a clean slate:
1. Shut-down your badge-software, and disconnect the printer from its power source;
2. Navigate to the Windows print center - accessible from the Control Panel as "Printers & Faxes" if Windows-XP, or "Devices and Printers" if Windows 7.
3. Right-click on your Zebra P110i printer, and select "See What's Printing" to open the queue, and see if there are jobs there. If so, click "Printer" on the menu, and then "Cancel all Document".
4. You also should ensure that you don't have any additional instances of the printer drive installed - they would show up as Zebra P110i (Copy 1), ... (Copy 2), etc. This occurs within Windows if you've disconnected the PC-end of the USB cord, and then plugged into a different USB port than originally used. If you have multiple instances, the easiest way to clean this up is to right-click on each sequentially, selecting "Remove this Device". Do this for each one.
5. Now you have a "clean slate". Connect the Zebra printer to the PC's USB, and then re-connect the power. If it doesn't power on, push the power button so it is on.
6. WAIT until Windows recognizes the pritner and you see the device is ready to use.
7. Open your badge software, and select a single card to print, and send it to the printer. If all goes well, this single card will print correctly, then the printer will come back to a ready status. Repeat for a second card, and make sure it prints correctly, and comes back to ready. If all is good, you've likely cleared the issues up, and you can proceed normally. If not, then there may be a physical problem with the printer, where it is not recognizing that a finished card has been ejected and the job is done, or it's not communicating that "done" status back to the host PC.