New Coverage issue detected in Blogger?

I got an email for one of my Blogger blogs saying: "Coverage issues detected on blog,
Warnings are suggestions for improvement. Some warnings can affect your appearance on Search; some might be reclassified as errors in the future. The following warnings were found on your site: Indexed, though blocked by robots.txt We recommend that you fix these issues when possible to enable the best experience and coverage in Google Search."

I have never blocked anything via robots.txt. I am not sure what to do. Has anyone else ever received this and did you do anything about it?