How to resolve? Pay back the $14K to the IRS. Now that letter you got has a phone number in it you can call for questions/additional information if needed. So if necessary you can call to see about setting up a payment plan with the IRS. But your words of "pay back" tends to lead me to think you got a refund of $14K or more. Hopefully it's not spent yet, and you can just send back $14K to the IRS.
Also, read that letter. I doubt it asked you to "upload" anything. You either have to mail the 1095-A and 8962, or fax it to them. It's important to follow the instructions in that letter to *absolute* *perfection*, or you risk finding yourself in a never ending nightmare with the IRS from which you will never awaken.
