NSX Upgrade and NAPP pages not loading with a spinning icon for a long time then an Error: "Something went wrong Failed to load. Please try again or contact support, if the problem persists."

Products

• VMware NSX

Issue/Introduction

• When selecting System -> Upgrade OR selecting NAPP from the NSX UI, there is a spinning icon or spinning wheel for a long time and then an error message:
  

  "Something went wrong 
  Failed to load. Please try again or contact support, if the problem persists."

• At the web page you will see similar images as below:
  
  
• These will eventually time out to the following error:
  

Environment

VMware NSX-T Data Center
VMware NSX
NAPP

Cause

• During the NAPP uninstallation process, the Helm repository projects.registry.vmware.com was not accessible, preventing some components from being removed cleanly. 
• Post-uninstallation of the NAPP, the NSX Upgrade page continued to show hanging/stale UI plugins

Resolution

• The NSX Upgrade page shows hanging/stale UI plugins
  • To resolve this, manually removed the hanging/stale UI plugins using the following commands:

    curl -k -H "Content-Type:application/json" -H "X-Allow-Overwrite:true" -u admin -X DELETE https://localhost/policy/api/v1/ui-controller/remote-ui-plugins/upgrade-ui
    curl -k -H "Content-Type:application/json" -H "X-Allow-Overwrite:true" -u admin -X DELETE https://localhost/policy/api/v1/ui-controller/remote-ui-plugins/platform-ui

• If this issue is accompanied with the NSX NAPP deploy, and the above DELETE command causes the NAPP page showing something similar to the following image, it may be necessary to force delete NAPP.
  
• NOTE: If NAPP fails similar to the above and force delete doesn't work, refer to KB How to force undeploy NAPP in NSX Manager

Additional Information

For further information:

• VMware NSX Application Platform 4.2 -- Page 153