In form 1095-A, column B in part 3 shows all months being 0.00, the app keeps rejecting that, saying it needs to be more than 0. How do I resolve this?

Use the Column B tax tool at Healthcare.gov to find the correct amount for column B; that link will take you there.  

Second Lowest Cost Silver Plan - Also known as SLCSP, this is reported on Form 1095-A in Part III, column B.   If you are eligible to claim the premium tax credit, the premium for a SLCSP that applies to some or all of your family members enrolled in coverage is a factor that determines the monthly amount of your premium tax credit.