Cannot open REST API link from Admin UI 12.7

Document ID : KB000113123
Last Modified Date : 18/09/2018
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We cannot open the REST API from AdminUI bottom URL Link. We get the following error
"Can't read swagger JSON from"

Same issue as this communities post:

How can I obtain the api-doc.war?
WAMUI 12.7.0

Please open a CA Support case for 12.7.0 WAMUI to receive the DevFix. 

You can also upgrade to 12.7.1 or 12.7.2. They both have the DevFix included.