Why does it say that I have already filed this year when I have not?

Did you by chance use the non filer portal on TurboTax or the IRS to register for the stimulus payment? If you did, a tax return form 1040 with 0 income was efiled for you to complete the registration. That portal was only to be used by persons not required to file a tax return.

If that is what you did, the normal course of action would be to prepare, print and mail an amended return form 1040X to file your "real" return. Some are suggesting that instead of going all the way through that process that you can just print your "real" return and write across the top of it "Amended Return". The IRS should process it that way. Follow the filing instructions printed with your return for what to include and where to mail it.