If your POS system is flashing device error at the bottom of the screen, it normally means that there is a problem with the printer directly attached to the POS terminal.
In the case of a device error, check the following:
The attached printer has power and is turned on.
There are no error lights flashing on the printer.
Make sure there is a paper roll in the printer and that it is seated correctly.
Check that the cable connecting the printer to the POS terminal is connected at both ends.
2. Initiate a printer reset as follows:
Power the printer off.
Hold down the feed button.
Power the printer back on with the feed button still held down.
The printer should reset and print a test docket.
3. If you still have the flashing device error, shutdown and restart the POS terminal.