It could also be if you signed up on the IRS non-filer tool to give the IRS your Direct Deposit Info for the Stimulus Check. If you did then see
https://ttlc.intuit.com/community/tax-topics/help/stimulus-how-to-file-your-return-after-getting-reject-r0000-902-01/01/1602609
So the only way to fix it is to send it in? By mail
If you're sure no one you know is claiming you, then your SSN may have been compromised.
Yes, you then have to file on paper to claim your own exemption.