There are numerous posts in the Blogger Help Forum about the disappearance of Earnings tab in the Blogger Dashboard. But it's not an error from the Blogger system, there's a reason behind it.
It's obvious to get worried when things are different from what it looks in general. The 'Earning' tab is basically in Blogger to help AdSense publisher connect or apply AdSense for their Blogspot blog. It just saves time and you can view your earnings up to date with the help of the Earnings tabs, it's for ease.
People new to blogs are unfamiliar with how Blogger and AdSense works, they can't usually differentiate between them and that is what creates the confusion. Blogger and AdSense are two different products of Google, AdSense has been integrated into Blogger for blogger users to apply for an AdSense account directly from their Blogger Dashboard and not only create an account but also check the earnings and stats.
You can check the Blogger Help guide 'Earnings tab' section to know more about it's terms and conditions
http://support.google.com/blogger/bin/answer.py?hl=en&answer=1269077
Or
Check the languages supported by AdSense currently
http://support.google.com/adsense/bin/answer.py?hl=en&answer=9727
It's obvious to get worried when things are different from what it looks in general. The 'Earning' tab is basically in Blogger to help AdSense publisher connect or apply AdSense for their Blogspot blog. It just saves time and you can view your earnings up to date with the help of the Earnings tabs, it's for ease.
People new to blogs are unfamiliar with how Blogger and AdSense works, they can't usually differentiate between them and that is what creates the confusion. Blogger and AdSense are two different products of Google, AdSense has been integrated into Blogger for blogger users to apply for an AdSense account directly from their Blogger Dashboard and not only create an account but also check the earnings and stats.
Why it's showing
Now you know that AdSense(which is the main component of the Earnings tab) and Blogger is different and their policies and terms are different too. The main reason as told by the Blogger support is that, if your language is not supported by AdSense then the Earnings tab won't be enabled in your Blogger Blogs Dashboard.You can check the Blogger Help guide 'Earnings tab' section to know more about it's terms and conditions
http://support.google.com/blogger/bin/answer.py?hl=en&answer=1269077
Or
Check the languages supported by AdSense currently
http://support.google.com/adsense/bin/answer.py?hl=en&answer=9727