It's hard to figure out what's happening without being able to see your tax return. (But don't post your return. This is a public web site that anyone can view.) Here are a couple of other possibilities. I should have thought of the first one before.
For 2018 through 2025, the total deduction for state and local taxes is limited to a maximum of $10,000 per year ($5,000 if you are married filing separately). The maximum applies to the total of real estate tax, personal property tax, and either state and local income tax or state and local sales tax. You might have hit this limit. If Schedule A line 5e is $10,000 ($5,000 if MFS) you have hit the limit, so no amount of additional sales tax or any other state or local tax is going to change your refund.
One other possibility is that you are already getting a refund of all the tax that was withheld, so there is nothing more to be refunded. Except for certain "refundable credits," you can't get a refund of more than you paid in.
You say "I am itemizing." Are you sure about that? Did TurboTax tell you that you are getting itemized deductions? Sometimes people think they are itemizing because they are entering itemized deductions, but their itemized deductions add up to less than their standard deduction, so they get the standard deduction. Only about 10% of taxpayers have itemized deductions higher than their standard deduction.
