PYEI EIC & ACTC was not given to a client

[Ismail]

I have a client who is income for

2020
W2: $7034.00
1099-G: $21,360 - paid $2136 fedral tax 

2019
W2: $26,217

MFJ with 4 dependents under 16 yrs old.

Expected refund: $11,690 based on usinf PYEI

Agjusted Refund : $5977.10 based on 2019 income 

Received letter from IRS regarding the adjustment but no explanation 

Am  I missing something here? and waht to do about? 

 

Thank you!