Tring to replace a COI 8, with a COID 8, went to memory block 7-1 card slot assingment, manual says to go of line press LK7 + LK1 use line key to enter setting data, it say's line key 6 for COID 8, when I press line key 6 it does nothing , what am I missing(not a NEC person)

Thanks for your help.