I am filing an amended 2021 1040 for a child whose mother filed for him and said he wasn't a dependent.  I have prepared the amended return like have a dozen or so others, but this one rejects with a message that the "1040X must be present in the return."  In the Homebase, the amended return column shows "Marked for EF".  

Can anyone suggest something to get this return filed?  I don't want to wait for a paper return.  The parents' return is holding waiting for this amended return to process.

Thanks for your advice.

Jim