Google Webmaster tools helps us detect problems that may not be very obvious to our human capacity.
But apparently, the problems they detect may not be intended. At least when we receive email notifications saying there are issues that we need to address. Once in a while I receive such emails notifying new accounts associated with certain websites or errors in crawling and increase in pages not visible to search engine crawlers. This is one of them.
But when I check the Google Webmaster account to verify and possibly fix the error, it seems that everything goes well as normal.
Maybe email came unreasonably too late, or that there’s a glitch in the mail system. Or maybe a revisit of the site proved earlier findings wrong. Hence, “No errors in the last 90 days. Nice!”.