"It is the second time that when I try to file electronically the system show an error that the file has a SSN or a EIN that has been previously filed, HELP to SOLVE"

If a return has already been filed with that SSN, your only option is to paper file the return.....seems a common theme these days that people got impatient waiting for their stimulus money and used the non-filer site which screws up the Efiling of their actual tax return.

I just got a rejected client. It said dependent's SSN has already been filed. But not by me.

The kid's 21 and in college. What are the odds that he filed his own 1040 and claimed himself, thereby screwing his parents of e-filing and getting their refund quickly?

Amending his by paper, and filing the parents' by paper during the shutdown? Priceless.

Refund? Don't hold your breath.