Ok, so I think you are missunderstanding this. In the PDF it is described very detailed. Do the following:
If you have build your system and downloaded it into your board, just don't close the window with the message "click cancel to stop using opencore plus ip timing remaining: unlimited"
In other words described, this message tells you: "you can now use/evaluate the opencore plus IPs in your system, as long as you don't click cancel"
To work with the open cores you leave that window open the whole time and keep the board connected to the pc the hole time. When you are exactly at that point there is no error, it is the wanted state.
leave that window alone and start building your NIOS System or whatever you want to test.
I hope this explanation makes it clearer to you. No error.
Good luck with your project.
