This indicates a printer error. It could be the result of a paper jam or some other problem that is preventing the printer from operating properly.
You should first try resetting the calculator by pressing the RESET button with a thin, pointed instrument.
If that does not work, then you should turn off the calculator, remove the paper roll, and ensure that the printer area is clear of any debris. You may want to blow compressed air into the printer area to see if anything is dislodged. After that, reload the paper and try again.
If you have done all of the above and continue to receive the error, then the calculator might require repair. You can contact one of the Authorized Service Centers listed at https://casiosupport.zendesk.com/hc/en-us/articles/5649253564185-Parts-and-Repairs if repair is needed.