I received the same error message code F8962-070.  My client did not use the insurance marketplace either.  Did you ever receive a solution?  I can't seem to find the reply.

Yes I did figure it out. He was on his parents insurance so that's why his SSN was flagged. You have to get the parent's 1095-A and the primary policy holders full SSN. Then you check the box on the Premium Tax Credit tab "other taxpayer will reconcile all APTC paid and this taxpayer is not taking the PTC (tax family size = 0)"

On the next tab you have to complete "Shared Policy Allocation (Form 8962, Part IV)"

Thanks so much for your reply.  He was on his parents insurance for January even though he was also covered by his employer's health plan, so that's what threw me off.  There was no matching SSN issue in 2020 because the premium tax credit was not required to reconciled, due to the pandemic, etc. so I didn't get this message last year either. 

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@rosemarie wrote:

 He was on his parents insurance for January even though he was also covered by his employer's health plan,

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It seems likely that you need to adjust the SLCSP on the 1095-A because of that (on whoever's return is claiming any of the 1095-A percentages).

YES I AM HAVING THE SAME PROBLEM, EVEN AFTER ATTACHING THE 8965 ACA EXPLAINATION AND IT STILL REJECTS.

@870ELaxxN What year are you filing this 8965 for? Are you sure you even need to file it?