1099-MISC income is preventing TTax e-filing

My wife and I are retired for about two years now. Last year she received a payment as the result of a class-action suit against her former employer. I've entered the 1099-MISC information into TurboTax but when I try to e-file I receive the following message:

 

"It looks like you have a tax situation in your federal return that makes it ineligible for e-filing, according to IRS rules. Here are the details: Your Earned Income Tax Credit (EITC) is based on non-documented earned income."

 

1) I cannot find anything on the IRS website regarding this rule. Is there a link where I can read about this?

 

2) Having entered the information from a 1099-MISC form why is TTax calling it "non-documented earned income"? By definition isn't a 1099-MISC considered a federal document?

 

3) Why is TTax categorizing the payment as EITC?

 

TIA for your assistance!