did you do a non-filer return to get your stimulus faster? if so you filed a 2019 tax return using your SSN. Thus your choices are to file by mail or wait to see if the IRS comes up with a method for taxpayers in your situation to e-file an amended return. If you didn't then someone else filed a return using your SSN. In this case, all you can do is file by mail. if you believe you're were a victim of identity theft include form 14039.