Are you referring to a Federal return? By any chance do you have a zero-income return, such as a filer with foreign earned income who used the FEIE to exclude all their income? If so, you cannot efile a zero-income return, but we can tell you a workaround so you can efile.
Also, if you haven't already done so, run the Federal REVIEW to see if any error messages are generated.
Is there anything unusual in regards to your return, such as a spouse who is not a US citizen or resident alien, etc.?