It's not letting me e-file because it says there's a mistake on my federal return. I've checked and everything is correct.

Yes, you may re-check the amount of disallowed sale and the code.  You can also try to do the following steps to fix the error.

1. Click Federal Review located on the upper right hand side of the screen .
2. Click review to each details ,and it will take you to form 1099.  
3. When done fixing, go back to Federal Review to check if the returns are ready to e-file.

 The errors on the return must be fixed in order to successfully transmit the return to the IRS and State.