I've been claiming my home office for years and this is first year being asked about prior depreciation amounts? I do my taxes with Turbo Tax?

There are two methods to calculate your home office expenses, one is the simplified method and the other one is the regular method. ‌Per the IRS tax tip, How small business owners can deduct their home office from their taxes:

• The simplified option has a rate of $5 a square foot for business use of the home. The maximum size for this option is 300 square feet. The maximum deduction under this method is $1,500.
• The regular method, deductions for a home office are based on the percentage of the home devoted to business use. Taxpayers who use a whole room or part of a room for conducting their business need to figure out the percentage of the home used for business activities to deduct indirect expenses. Direct expenses are deducted in full.

You have probably used the simplified option in the past.  This method doesn't use depreciation of the home. When you are entering the information in TurboTax there's a question where you select what method you want to use. If you want to continue using the simplified method, you can go back through your entries and change this.   

Can I take the home office deduction?

Where do I enter the home office deduction for my business?