1. After the printer is connected, press and hold the PUASE key to turn it on, and then let go when all the lights in front of the printer are on to see if the test page can be printed. If so, the printer is fine. 2. See if there is any problem with the data connection cable. Try replacing the cable or port. The LTP port commonly used in Zebra 105SL printers is prone to problems. You can try changing the serial port. 3. See whether your software selects the machine of 105, whether the printer is used offline, and whether the printer driver port is selected with your connection port. Eliminate them one by one, and it will be easy to find the problems.