I'm trying to enter my actual expenses and the program is not allowing me to enter my vehicle expenses.

You can try a few things to get the system working.

I suggest logging out of your TurboTax Online account and clearing your browser's cache and cookies.  You can also try using a different internet browser to log into your account to see if this remedies the issue

How to Clear Cookies, Cache History

Also, remember that in 2017 and earlier tax years, employees could get a partial deduction for expenses incurred while commuting between multiple job sites during the same day, as well as commutes to temporary work locations. They could also claim costs for non-commuting work-related trips, such as attending an offsite meeting or running an errand for the company. However, these expenses are no longer deductible in tax years 2018 through 2025 due to the Tax Cuts and Jobs Act (TCJA) that Congress signed into law on December 22, 2017.