After exiting unfinished course, it doesn't resume properly

It's hard to troubleshoot without seeing the .story file. Best guess: You have a trigger that disables the Next button when the timeline starts. That trigger runs again, even if you have the Slide Properties set to "Resume saved state." 

To prevent that from happening, add a condition to the trigger. For example, use a condition that checks whether a T/F variable = False. Also add a separate trigger that changes the variable to True when the interaction is completed. 

• The file in this post demonstrates how to do this: TIP: Controlling the NEXT Button 101 - Articulate Storyline Discussions - E-Learning Heroes