Yes, the loss was correctly reported on Line 14.
You should NOT have entered anything on Line 21 of your 2017 tax return. You should have left that blank. Then Line 41 would be negative, which is correct.
Once you amend to get rid of that Line 21 entry, Line 41 should be negative. That then allows you to claim the NOL in other years.
*IF* you filed your tax return on time and included the proper statement to "waive the carryback" of the NOL, then you would need to MANUALLY calculate the NOL and enter that on Line 21 of your 2018 tax return. If you did not file your tax return on time, you can't include that statement to "waive the carryback", so you would need to amend your 2015 tax return (or file Form 1045 by December 31st). Again, TurboTax does not do the calculation, so you would need to MANUALLY calculate the NOL.
You may also consider going to a tax professional.
