Accu-Chek Performa Operator's Manual page 52

The meter is not coded or the code
chip is not inserted. Turn off the
meter and recode it.
The test strips will expire at the end
of the current month. At the end of
the month, discard the code chip and
any remaining test strips. Insert a
new code chip from a new box of
50
test strips and ensure the code chip
number matches the code number
on the test strip container. Make sure
the time and date in the meter are
correct.
The test strip is damaged. Remove
the test strip and reinsert it or
replace it if damaged. Or the code
chip is incorrect. Turn off the meter
and insert a new code chip. If the
message reappears, contact Roche.
The code chip is incorrect. Turn off
the meter and insert a new code chip.
If this does not fix the problem,
contact Roche.