Received a Reject code R0000-902-01 filing form 4868 extension for a new client this year.

Taxpayer TIN in the return header must not be the same as a TIN of a previously accepted electronic return for the return type and tax period indicated in the tax return.

Could this be an extension form 4868 was previously filed or would they be stating a Form 1040 was previously filed? 

That is my question.