If an appraisal rebuttal is unsuccessful, you have a couple of options that you can pursue. You can proceed with the loan at the appraised value given on the report if the loan still works for you, or you can decide to cancel your loan and let the appraisal expire. Once the appraisal expires, you could decide to try again with a new application, FHA case number, and appraisal. Keep in mind that letting an appraisal expire is a lengthy process with no guarantee that the next appraisal will be more favorable to you value wise, as the market conditions can change in 6 months.