FILED 4868 IN APRIL. NOW CAN'T TRANSMIT RETURN DUE TO DUPLICATE SSN.

[Just-Lisa-Now- · Accepted solution]

Has nothing to do with you filing the extension.  That means someone else already filed a return using that SSN, you will be paper filing the return.

Look at the clients Form 9325 to be sure you didnt file the return when you filed the extension.