Unreimbursed employee business expenses are no longer deductible under the new tax laws unless you fall into one of the 4 categories below. This is why you are seeing zero after entering your mileage for your federal.
A few states still allow this deduction. If you are in one of those states you will see it on your state return.
"You can no longer claim a deduction for unreimbursed employee expenses unless you fall into one of the following categories of employment, or have certain qualified educator expenses.
Armed Forces reservists.
Qualified performing artists.
Fee-basis state or local government officials.
Employees with impairment-related work expenses." https://www.irs.gov/publications/p529#en_US_2018_publink10003917
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