The $600 you received in January was for the second stimulus payment which you would have reported receiving on your 2020 tax return, not the third stimulus payment which is reported on your 2021 tax return.
The third stimulus payment would have been sent to you in the March - May 2021 timeframe.
Look at your bank deposits during the time. If it was received the payer would be IRS TREAS 310 TAXEIP3
