Google AdSense may have a bug with its PIN verification processs. There are tons of AdSense publishers complaining in the Google AdSense Help Forums about issues where they are unable to use the PIN verification anymore. It seems like a widespread bug but I am not sure, as Google has not responded to those complaints.
Dwayne Cubbins from Tech Issues Today reported this yesterday. He wrote:
A growing number of publishers and content creators are running into roadblocks with Google AdSense. They’re dealing with failed identity verifications and PINs that never show up in the mail. This is leaving many stuck without payments, even after hitting earning thresholds.
And if you scan through Google AdSense Help Forums and you'll see a lot of these complaints throughout the forums.
Here are some screenshots of the issues:
A Google AdSense product expert wrote in this thread wrote:
Yes, the PIN troubleshooter appears to be broken. A lot of publishers have reported this problem.If you've run out of options to ask for a replacement PIN, all you can do is wait and hope that one of them eventually reaches you.
So if you are having these issues, know you are not alone - it seems like it might be a bug with Google AdSense.
Forum discussion at Google AdSense Forums.