A home appraisal fails when it issues an appraised value that is less than the home purchase price. Several factors can fail a home appraisal, including sluggish housing market conditions, bad comps, and inexperienced appraisers who don’t possess adequate local market knowledge. Messy and blighted homes can also fail an appraisal. This is why sellers are encouraged to clean up their properties beforehand and give the exteriors a bit of curb appeal.