The panel for Background Tasks can be found in a submenu of the Windows menu:
(from my German InDesign where Background Tasks is called "Hintergrundaufgaben")
What exact version of InDesign are you using? On what OS version?
Are there any error messages?
You can try to tackle the problem with a "Divide-and-Conquer" method if the error lies in just one or a couple of pages. First export one half of your pages to PDF. If that will not fail try the other half. In case you get a problem, narrow down the page range.
In an older thread I presented a script that is able to use the "old" method of exporting PDFs without using the background process (like done with InDesign CS4 and below). That script is still working with CC 2015.4.
Did you find the culprit?
Coming back here with a solution might be interesting for other users with similar problems.
Thank you so much for responding. I was in a panic because of my deadline. I did not solve the problem but I was able to upload to the printer in InDesign.
"My mission is to create art that reflects the beauty of my people and the stories of our lives and communities."
Sent from my iPhone