Arlene Lee of AdSense Publisher Support posted on the official blog an update of the AdSense customer channel error. Arlene reported that -
"Over the past few days, some publishers let us know that they were unable to view any data for their custom channels. Our engineers have now resolved the issue, and they're currently working on including the missing data from the past few days.
Your custom channels should now be tracking data as normal. Please be assured that your aggregate reports, which are used to calculate payments, have not been affected."