How to link separate Excel files to auto-populate cells

This should work (it did work in my testing):

Open the Master file
Open the csv file
Copy this formula to cell H2.

Formula:

=LET(Mdata,     TRIM('C:\Test\[Example_Mastersheet.xlsx]Sheet1'!$A$1:$D$95),

 MA,INDEX(Mdata,SEQUENCE(ROWS(Mdata)),1),     MB,INDEX(Mdata,SEQUENCE(ROWS(Mdata)),2),

 COut,IF(F2<>"",FILTER(Mdata,MA=TRIM(F2),""),IF(G2<>"",FILTER(Mdata,MB=TRIM(G2),""),"")),IFERROR(INDEX(COut,,{3,4}),""))

Adjust the file location, file name, sheet name and range in the first line of the formula.

Copy the formula in H2 down to the bottom of the csv file.

Save and close the csv file.