I did a little more testing and came to realize what I think is my issue. I logged into the WebFOCUS application using Chrome but when I clicked on the Excel drilldown link, I never paid attention to the fact it opened up in Edge (which is set as my 'default' browser). Edge doesn't have a session so naturally I was prompted to re-authenticate. From Excel I copied the drilldown link and pasted it into my current Chrome session and the drilldown worked. I then changed my default browser in Windows to use Chrome and the drilldown link from Excel opened successfully in Chrome.
I also corrected the drilldown link syntax, but it is important to note that even with the FOCEXEC=app/jwxu52ru.fex syntax, the drilldown works from Excel.
This was the original code in the FEX stylesheet -
TYPE=DATA,
ACROSSCOLUMN=N1,
FOCEXEC=app/jwxu52ru.fex(PROGCODE1=N1 ORGNCODE3=N3 ACCTCODE2=A3 ATYPCODE1=A1 COASCODEKEY='1' FSYRCODEKEY='&FSYR_CODE_KEY'),
$
I changed the code to -
TYPE=DATA,
ACROSSCOLUMN=N1,
FOCEXEC=IBFS:/WFC/Repository/frsnrc0w/Position_Control/jwxu52ru.fex(PROGCODE1=N1 ORGNCODE3=N3 ACCTCODE2=A3 ATYPCODE1=A1 COASCODEKEY='1' FSYRCODEKEY='&FSYR_CODE_KEY'),
$
Thanks for pointing me in the right direction. I'll do some more testing to confirm this is working.
-Doug