"I am just giving you different scenarios"

Your clients didn't "miss" EIP 1 or EIP 2. They missed the Advanced Payments of the EIPs. These payments were computed using the tax return info for 2018 or 2019, as a Best Guess by the Feds for projecting what your clients will qualify for in 2020. The payments are part of a recovery plan for 2020. Actual Tax Return data will be used in 2020 as a reconciliation function. We were impacted in 2020. Everything applies to 2020 actual events.

So, your clients need to file a factual 2020 return. They got $0 for any payments, so you will put $0. And the 1040 will show if they are now qualified for $.

I hope this helps you think it through.