SH match not deposited for 2020

Small SH 401(k) plan (one MD, six NHCEs) had balance due for 2020 Safe Harbor match.  As of mid-2022, the 2020 SH match not deposited to plan (pooled account).  What options does the plan sponsor have to correct this?

Thanks.

Some years ago we had a plan with this situation and decided that, because it was a required contribution, it could be self-corrected by depositing the money now with earnings. I don't recall if there was a clear example like this in EPCRS or if it was a stretch.

I believe for self correction, under these facts and circumstances and assuming a 12/31 PYE, the plan must be corrected by 12/31/2022.