Did your dependent file a tax return and claim themself? Or it could be an honest mistake on someone else's return. They may have entered the ssn wrong and got yours. If your return rejects you will have to print and mail it this year and let the IRS figure it out.
How to mail a return from the Online version
https://ttlc.intuit.com/community/printing/help/how-do-i-print-and-mail-my-return-in-turbotax-online...
Be sure to attach copies of your W2s and any 1099s that have withholding on them. You have to mail federal and state in separate envelopes because they go to different places. Get a tracking number from the post office when you mail them for proof of filing.