Many taxpayers are surprised this year because their itemized deductions are not having the same effect as they did on past tax returns.  The new higher standard deduction and the elimination of certain deductions, as well as the cap on state and local taxes have had a major impact.

Your itemized deductions have to be more than your standard deduction before you will see a change in your tax owed or tax refund.  The deductions you enter do not necessarily count “dollar for dollar;” many of them are subject to meeting  tough thresholds—medical expenses, for example, must meet a threshold that is pretty hard to reach.  The software program uses all the IRS rules that apply to the expenses you enter, and it tells you if you have enough to use your itemized deductions or if using the standard deduction is more advantageous for you.  Under the new tax laws, some deductions have been capped—there is a $10,000 limit to the itemized deductions for state, local, property and sales taxes.

Your standard deduction lowers your taxable income.  It is not a refund 

2018 Standard Deductions:

Single   $12,000  (+ $1600 65 or older)

Married Filing Separately    $12,000  (+ $1300 65 or older)

Married Filing Jointly  $24,000  (+ $1300 each spouse 65 or older)

Head of Household  $18,000  (+ $1600 65 or older

Look at line 8 of your Form 1040 to see your standard or itemized deductions.

https://ttlc.intuit.com/questions/4482873-which-federal-tax-deductions-have-been-suspended-by-tax-re...

This answer does not help at all.  I still had greater than 24k of itemized deductions....even with a 10k cap on property & sales taxes.  

are there thresholds in place for home office (business) expenses and charitable contributions as well?

Unreimbursed employee business expenses are no longer deductable.  Business expenses on a Schedule C are irrelevant for itemizing.  Charitable deductions are capped at 60% of income.

With 10k of prop tax (max limit), ~11k of mortgage interest, ~6k in charitable contributions and a few other pots and pans the standard deduction should not be used as that is 27k itemized.   Yet, TT still employed the standard deduction.  Doesn't make sense.....

You're going to have to go through Schedule A item by item to figure it out.  Almost no chance it is a TurboTax error.

If you are using the CD/download version you can switch to the forms mode and vie the Schedule A to see the calculations.

You can also check the actual amount of itemized deductions by using the Search Topics for "itemized deductions, choosing" (under "My Account, Tools" in the online versions).    Click on "Change my deduction". That will display the actual amount of itemized deductions vs. the standard deduction.    (Be sure to uncheck "Change my deduction" after checking it so you do not lock in the wrong deduction.

For the Desktop program
If it's giving you the Standard Deduction and  not showing you Schedule A you have to switch to Forms Mode and open A from the top of the left column Open Form and pick schedule A out of the list on the right side.

See my screen shot on this one.
<a rel="nofollow" target="_blank" href="https://ttlc.intuit.com/questions/4679612-schedule-where-is-schedule-a-i-am-itemizing-property-tax-m...>

For either the Desktop program or the Online version....
You can check the actual amount of itemized deductions by using the Search Topics for "itemized deductions, choosing" (under "My Account, Tools" in the online versions).    Click on "Change my deduction". That will display the actual amount of itemized deductions vs. the standard deduction.    (Be sure to uncheck "Change my deduction" after checking it so you do not lock in the wrong deduction.