Tax Year Prior to 2020: Why is my home office deduction not allowed even though it is used 100% and exclusively for my business?

Make sure you have a net profit for your business.  Your "net" profit is the amount after expenses.  This would include vehicle expenses, advertising, supplies, etc.  If you still had a net profit after that, you should get the Home Office deduction.  You can check your net profit by previewing your 1040.  Line 12 of your 1040 will show the business profit or loss.

How do I Preview my TurboTax online return before filing?

https://ttlc.intuit.com/replies/3302322

The answer to this question was to check "net profits", if there were none, then I wouldn't get the deduction. However, the last 2 years I've had no net profit and still got the  home office deduction. Please explain. Even if the money to cover the business expenses didn't come from the business, they were still paid (personal funds). I should get the deduction.