Tip: If you have ethernet issues you can connect your printer to your iPad with a USB-C cable and get instant connection to continue printing guest bills. Equally, your iPad can jump on your phones personal hotspot and you are able to service your customers as normal.
The first step to check if the printer is blinking and not printing
Do you have paper in the printer? If not put a new roll into the printer and voila.
If it's still not working consider the options below depending on your connection type.
Connection with a USB cable
Unplug the cables and plug them in again by swapping them around
Check if you cable is damaged and in this case replace it
Connection with Ethernet cable or WiFi
If your printer is blinking green it means it has lost connection and you need help it get back online. Turn it off and on first and see if the green light is constant. Then it works again. If not:
Check if your router is online and your other devices can connect to the ethernet/Wi-Fi. If not try to find a cable to connect the printer to get it to print while you sort the ethernet connection.
Unplug your ethernet cable or Wi-Fi dongle completely and connect them again. Turn off and turn your printer.