plu no data err on a sams er5215sm?

all the department keys we set up work except key number 3 and number 4...the rest work as programmed.
is this a board problem or chip error?
We do not use plus...we simply enter the price of the items into the register...cannot delete the plu programing. The two keys in question are labeled plu 3 and plu 4 when we did a self test