You are no longer claiming a passive loss on the 2015 and 2016 returns.  You are claiming a net operating loss.  Your post states that IRS wants an amended return for 2017, but that's the NOL year, right?  What was done with the NOL when it was not carried back?  Was it claimed on 2018 on later years?  And why is IRS looking at 2017 just now?