If you install from 0 following this tutorial, you no longer have to do that.I had something similar previously with adding the Facebook custom app. What I had to do was install some of the previous versions and go through the process of adding the custom app. When it worked and my account was added, I exported the settings and imported into the new update.
Can I ask where you found out where to create the custom app for LinkedIn? I couldn't find how to set up for the app ID and api ID.
Check tutorial:
Regarding LinkedIn I don't use it in my country so I can't help you with that. :/