you don't say what happened in 2015-2017 or whether you had more than one property during any of the years.   however, IRS rules would require you to report the loss carryforward on the 2015 return , still loss on the 2016 return, still loss on 2017 return and then still loss on 2018

then because the property is sold you would get whatever the loss carryforward is

so start amending with 2015 if you ever want to utilize the 2014 loss and be sure that the IRS allows it.