What are you really trying to do? Did you file a 2020 return that was accepted and processed by the IRS? Or was it rejected and now you are hoping to try again to file it? If so, it cannot be e-filed. The only way to file it is by mail, and it is too late to receive a refund for a 2020 return now. If you owe tax due, you are also going to owe late penalties and interest.
You are asking about form 8962 which is the form you need to include by entering your 1095A for having marketplace health insurance. Did you have marketplace health insurance for 2020? You have to get the 1095A from healthcare.gov.