Why won’t it allow me to enter in both box 3 and 7 on a 1099-MISC?

You should be able to enter a 1099-MISC with entries in both boxes 3 and 7.  Delete the form and try again.

 

To delete the 1099-MISC please follow these steps:

 

TurboTax Online

1. While in your return, click on Tax Tools > Tools (in the black bar at the side of your screen).  
2. In the Tools Center, under Other helpful links click on Delete a form.
3. Click Delete next to the form you want to delete and follow the onscreen instructions. 
4. Once you have finished deleting the desired form(s) click the Continue with My Return box (in the lower right of your screen).

TurboTax CD/Download

1. Go into Forms Mode by clicking on the Forms icon in the top right of the blue bar. 
2. In the Forms in My Return list on the left, click on the form you wish to open and delete.
3. Click on the Delete Form box at the bottom of the screen.
4. To return to the interview, click on the Step-By-Step icon in the top right of the blue bar.