Nested IF / IFS Function

Hi - I'm trying to compile some KPI reporting but struggling to get the right combination of nested IF functions (and also tried IFS to no avail).

I need to show:
If an order is sent to the warehouse before midday on any given day, the pack slip must be returned on the same day to "PASS", otherwise "FAIL".
If an order is sent after midday on any given day, the pack slip must be returned by the following day to "PASS, otherwise "FAIL".

So far I've got the following:

Column C = sent date
Column D = before midday (Y/N)
Column E = return date

=IF(D2="Y",IF((NETWORKDAYS(E2,C2)-1)=0,"PASS","FAIL"),IF((NETWORKDAYS(E2,C2))=1,"PASS","FAIL"))

Above formula returns "PASS" if dates are equal regardless of whether D = "Y" or "N". What is missing?

Thanks in advance for your feedback,
Simon