I'm not getting the same numbers as I used to?

Please check the following:

Does your instrument display an error when calibrating?
Are you sure that you are comparing numbers in the same numerical system; ie., Lab, Lch, etc.
Are you using the same illuminant and observer settings?
Do you have the aperture set correctly? (see Related Support)
Have you tried resetting the instrument? (see Related Support)

If none of the above helps, the instrument requires service.