I used Biotek Epoch 2 nanoplate reader for quantification of my nucleic acid samples. I do not understand what does the above mentioned statement signify.
This plate reader has 2 detector photodiodes, one for measurement and one for reference. I think that the error message means that the absorbance recorded by the reference photodiode is higher than the acceptable upper limit. This might happen if the reference diode is blocked by something, if it has failed, or if the sample absorbs too strongly at the reference wavelength.