Our Samsung ER 5200 has on the screen 'PCo', no key is functional and we have tried to unplug and turn off with no results. We only use the machine on weekends, and it is unplugged during the week. It worked fine last weekend. Any help would be appreciated

Kathy Stalwick, October 2014

Hi. Printer Cover Open :-)
Make sure the printer cover is on. There will be a piece of the printer cover that pushes a switch somewhere to tell it that the cover is on. If that doesn't work, there is a manual for this model on the net:

https://the-checkout-tech.com/manuals/cashregisters/Samsung2.php

Registerman, October 2014