I have entered all my information how do I get the system to update my tax due ?

If you are entering itemized deductions, the amount of tax due will not change until the total of all your itemized deductions exceeds the amount of the standard deduction for your filing status. There are limits or thresholds on several itemized deductions. For example, you can only deduct the amount of medical expenses that exceed 7.5% of your AGI. The amount of real estate, state income, and other deductible taxes in total that can be deducted is limited to $10,000. 

Here are the standard deductions for each filing status:

Single - $12,200 add $1,600 if age 65 or older
Married Filing Separately - $12,200 add $1,600 if age 65 or older
Married Filing Jointly - $24,400 add $1,300 for each spouse age 65 or older
Head of Household - $18,350 add $1,600 if age 65 or older

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.