It could be that the Standard Deduction is still more than all your itemized deductions.
Or maybe you are already getting back all that you can and more deductions won't increase it.
Itemized Deductions or the Standard Deduction can only reduce your income to zero and not create a refund. Then you only get back any withholding taken out.
TurboTax starts off using the Standard deduction, so until your Itemized Deductions are higher than the Standard deduction your refund would not change. Or it will just change a little at a time as you increase your deductions over the standard amount.
And by increasing your deductions it will decease your income and you may not be getting as many credits as before. Also after you reduce your income to zero there is no more refund to get back but you still may owe for other things like self employment tax or the 10% early withdrawal penalty from 401k or IRA accounts.
