When trying to connect to WebCenter via iPad/iPhone, you get an error because your URL is not (no longer) correct. This article describes how to modify the saved URL to point to the correct WebCenter address.
You receive the following error when trying to connect via iPad/iPhone:
URL (http://yourWebCenterURL.com/WebCenter_Inst/) is not a valid WebCenter Instance or you don't have a good connection to this URL.
Please check the correct spelling or check in Safari if you can browse to this URL.
To solve this problem, delete the account and re-add it with the correctly formatted URL:
From the main page, choose Manage Accounts.
Swipe left on your listed account and delete it.
Tap the + icon to add a new account.
Type the URL exactly as it's displayed in your web browser. This is case sensitive. Do not add anything after the instance name (e.g. /homepage.jsp or /login.jsp).