Based on my internet research, it seems like a portion of the purchase should be able to be written off, but TurboTax is disagreeing thus far. Looking for clarification.
It depends. You can use depreciation to expense your car. It fact, according to this IRS.gov link, you can claim vehicle expenses two ways. You can use standard mileage that has a depreciation equivalent built into the mileage rate or you can use actual expenses, which includes an accelerated depreciation method.
If you are trying to recoup the cost of your car, you would use the the Modified Accelerated Cost Recovery System (MACRS). If you use mileage the first year, then you will need use the straight line method to claim your depreciation if you choose to use actual expenses after that first year.. In fact, this IRS link explains thoroughly how to use depreciation to expense your car.
Please refer to this IRS link, for additional information.
Understand that the cost of the vehicle is never a "permanent" write-off. You report/claim the vehicle in the Business Vehicle Expenses section. You may or may not qualify for the SEC 179 and/or Special Depreciation allowance, which allows you to depreciate up to 100% of the cost in that first year. Just work it through, and based on your input the program will "know" what you qualify for and present you those options to either take or decline as you choose.
My recommendation is that if your business does "NOT" have the taxable business income from which you take the SEC179 or SDA, then don't take that option (at least not 100% of it) if it won't benefit you tax-wise on your 2020 tax return.