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The the reason for this seems to be that the page is trying to resolve a internal load balancer address, and not the external facing client side load balancer that the browser can access. To fix this, do the following steps:
Go to the BPEL process of the specific composite in Enterprise Manager. Then click on the Human task under the Component Metrics tab.
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You’ll then see the internal address and port that cannot be resolved from your web browser.
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Replace these with the external address as well as port. (Most probably the one used when accessing the Worklist app url) Click “Apply”
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Your Worklist app should now load.
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Credit: Thanks to my colleague Ben Taljaard for helping to solve this issue.