I have multiple 1040 extensions rejecting today with the following error:

Error Message: 'ReturnTypeCd' (specified in the Return Header) and the return version (specified by the 'returnVersion' attribute of the 'Return' element) of the return must match the return type and the version supported by the Modernized e-File system.

Solution: The IRS will not accept an e-file extension for a return unless the return being extended is for the current tax year, and the extension is filed before the return's original due date.

Code: R0000-004-01

I've filed lots of extensions (we extend every return), and I've never gotten this error.