Trouble using IFERROR with an IF statement that has Multiple Conditions

I have a nested IF formula. The return value for some of the IF statements is given by index-matching. If the item doesn't exist on the other sheet, the index-match returns a #N/A, but if there's an error I want the cell to say "Needs Investigation" instead of #N/A, so I've put in IFERROR statements to do this. This works fine. See the first IF statement I have emboldened to see what I'm talking about.

The issue I'm having is with the last IF statement (also in bold). This one is different from all the other because it has multiple conditions (one of which is given by index-matching) and because I specify an Else return value (i.e. If condition is true, then return value, else return other value). I want to achieve the same thing as above (that is, if the same #N/A error occurs as above I want the cell to say "Needs Investigation" instead of #N/A). I've put in IFERROR statements everywhere I can think of, and nothing works. Where should I be putting in IFERRORs? Or should I be using something other than IFERROR?

=IF(D2="Approved","Approved",IF((AND(D2="Supplier Submittal",E2="Interim Approval")),"Interim Approved",IF(D2="Define","Initial Review",IF(D2="Due Date Approval","Initial Review",IF(D2="Initial Review","Initial Review",IF(D2="No Status","Drawing Not Released",IF(D2="Polaris Review","Polaris Review",IF(D2="Staging","Waiting on Child Components",IF(D2="Supplier Acceptance","Initial Review",**IF(D2="Closed W/O Approval",IFERROR(INDEX(SharePoint!X:X,MATCH('Exceptions List'!A2,SharePoint!N:N,0)),"Needs Investigation")**, IF(D2="Needs Validation",IFERROR(INDEX(SharePoint!X:X,MATCH('Exceptions List'!A2,SharePoint!N:N,0)),"Needs Investigation"),IF(D2="No PPAP Required",IFERROR(INDEX(SharePoint!X:X,MATCH('Exceptions List'!A2,SharePoint!N:N,0)),"Needs Investigation"), IF(D2="Transferred",IFERROR(INDEX(SharePoint!X:X,MATCH('Exceptions List'!A2,SharePoint!N:N,0)),"Needs Investigation"),IF((AND(D2="Supplier Submittal",C2<TODAY())),"Supplier Late",IF((AND(D2="Supplier Submittal",C2>TODAY(),C2<$J$1)),"On Track for PV",**IF((AND(D2="Supplier Submittal",C2>$J$1, INDEX(SharePoint!X:X,MATCH('Exceptions List'!A2,SharePoint!N:N,0))="")),"Due after PV",INDEX(SharePoint!X:X,MATCH('Exceptions List'!A2,SharePoint!N:N,0)))**)))))))))))))))

Here's the same formula, probably easier to look at.

If it helps, here's an example of the the first IF statement I emboldened (the one that works) from the spreadsheet.

And here's a snapshot of an example of the IF statement I'm having trouble with.