I enter the amount reported in box 3 1099-INT but when I go to adjust the taxable amount for previously reported interest and enter the amount of interest previously reported it does not change the total amount of taxable interest from the amount reported

You have to enter the adjustment as a positive number to have it deducted from the amount entered from your Form 1099-INT. I'm not sure where you a looking to see what amount of the interest is showing as taxable. You need to look on line 2b on your Form 1040 for this. 

To view your form 1040 and schedule 1 to 3:

1. Choose Tax Tools from your left menu bar in TurboTax Online
2. Choose Tools
3. Choose View Tax Summary
4. See the Preview my 1040 option in the left menu bar and click on it
5. Choose the Back option in the left menu bar when you are done