Microsoft Azure - Troubleshooting - Invalid Application key error in AD Application & Service Principal mode

Microsoft Azure - Troubleshooting - Invalid Application key error in AD Application & Service Principal mode

"Azure Services discovery failed for subscription <subscriptionID>. Invalid Application key" - Error message upon editing a New Azure monitor using AD Application & Service Principal mode

Troubleshooting:
In AD Application & Service Principal mode, the user creates an AD Application in Azure portal and provides the portal generated the keys ClientID, TenantID & Application Key in Applications Manager. After 1 year of creating it, the Application Key expires and throws the above-mentioned error message. 
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In this case, the user has to log in to Azure portal, go to 'Azure Active Directory' -> App registrations -> Select 'All apps' -> Click on the application created by the user -> Settings -> Keys -> Delete the expired key -> Create a new one by giving 'Never expires' -> the key will be displayed upon saving -> Copy the key and update the same in the "Application key" field of AD Application & Service Principal mode and update.