Late Filing - IRS Letter

Had a potential client come to us who found out their 5500s were never filed for 2020 and 2021 because they say they never had reminders or communications from ADP. They immediately filed them when they found out in September 2024, but did not file thru DFVCP. They then received notice CP 283. It is a small plan and those penalties are hefty, so they are looking to see how they can reduce. I checked EFAST and I don't see filings for two other years, and late filings (by a couple of weeks) for two additional years but unsure if they ever received notices regarding that.  1) Is it even possible to refile 2020 and 2021 through DFVCP?  2) The reasons for being late are typical from COVID - anyone have any success with penalty abatement?

Here is a recent chat that may help.