Rental Property Asset Depreciation

Turbo Tax Home & Business is indicating $0 depreciation on rental property purchased  in 2012.  Have entered required land purchase and building costs and date of acquisition.   Next window required entering previous depreciation amount taken which  I entered, software went into calculation mode and came up with $0 depreciation.  My understanding is the depreciation schedule for this type of asset is 27.5 years.  Has tax law changed  regarding this, or is there another reason the depreciation I have received in prior years is not showing up?