Why is my EpiTect Methyl qPCR Assay "failed" as indicated in the QC page of the data analysis Excel file?

That is because the Ct difference between mock digestion and double digestion is less than 2, which means that less than 75% of the input genomic DNA is resistant to the digestion. Therefore, the result from such digestions is unreliable in DNA methylation analysis. So we labeled such an assay as failure and exclude it from data analysis.