Unfortunately, if you are an employee (Paid with a W2 not a 1099), beginning with your 2018 Tax Return, you can no longer deduct your employment related expenses.
The Tax Cuts and Jobs Act (TCJA) that was signed into law in December of 2017 eliminated all "Miscellaneous Itemized Deductions" formerly allowable on your Schedule A. This includes all "unreimbursed employee expenses" including business mileage.
For more information on this new limitation as well as other changes that may have an effect on your return, check out this TurboTax FAQ: How Will New Tax Legislation Affect My 2018 Tax Return?
Because all deductions must be entered inti the Federal interview and they carry to the state (if any). Several states still allow that deduction. TurboTax has no way of knowing in advance if you will add a state that has that deduction, so if the question is not asked you might loose out on a state deduction.