2463881 - Portal UI Theme Designer not working after upgrade due to blank screen including red blocked cursor

• After a Enterprise Portal upgrade the UI Theme Designer results in a blank screen similar shown below:
  
  
  
• You may also see an alert pop up The parent window did not answer when requesting the origin. as below:
  
  
  
• If you do not see the alert pop up above, you may see an error in red text in the Console similar to below:
  
  Reached timeout of Xms waiting for a response from parent window -  sap/ui/security/FrameOptions
• The UI Theme Designer displays correctly however you cannot interact with it and your cursor changes to the following:
  

Image/data in this KBA is from SAP internal systems, sample data, or demo systems. Any resemblance to real data is purely coincidental.

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