Unable to renew existing coverage—The Marketplace determined that you were notified that your health insurance policy was not renewable and you considered the other plans available to be unaffordable.
Eligible for health coverage tax credit (HCTC)—You were eligible for the health coverage tax credit in the month. (For this purpose, you are considered eligible for the HCTC if you would have been eligible had you enrolled in HCTC qualifying coverage.) This exemption is available only for July through December of 2016.
Cannot find this exemption for 2017
https://www.irs.gov/pub/irs-dft/i8965--dft.pdf