I am getting message that the marketplace policy number is a duplicate.. Marketplace said it is not a duplicate. How do I resolve this issue?

It may be an input error as far as an extra character or space that is generating the error.

I recommend reviewing your information for your 1095-A form as follows, deleting the entry, and then re-entering it.

Go to your Federal interview section. 

1. Select Deductions & Credits 
2. Scroll down to All Tax Breaks 
3. Select Medical 
4. Select Affordable Care Act (Form 1095-A)

You should see a list of any policies here.  Select the delete to the right of the policy to delete it.

Then go ahead and select +Add another to re-enter the 1095-A information.

This may rectify the issue and allow you to proceed with your input.