Sometimes InDesign crashes without for no apparent reason. This almost always causes an exception in Publishing Assistant because PA requires InDesign for its work. There are no perfect solutions, but a couple things you can try:
Idea #1 – restart Windows
Click Windows > Power > Restart. Starting with Windows 10, it is no longer good enough to shut down Windows each night. In order to start faster, when you shut down Windows 10, it stores on image on your hard drive for faster loading when Windows starts the next time. This image may contain problems that can only be cleaned out by doing a complete restart.
If you want you can change this behaviour in Windows 10 by going Control Panel > Power Options > Choose what the power buttons do > Change settings that are currently unavailable > uncheck “Turn on fast startup (recommended)”. This means, when you do a shut down each night, you get a fresh load of Windows the next morning.
Idea #2 – reset InDesign
Open InDesign in the way that you normally do. Immediately after clicking to start InDesign, hold down the <Shift>, <Ctrl>, and <Alt> keys all at the same time. As InDesign starts you should get a message asking “Delete InDesign Preferences Files?”. Click on the Yes button.