I managed to get my OneDrive backups working yesterday but forgot to update this post. - my apologies for the delay.
The confusion is that there are several different Microsoft character strings that are involved and the naming is inconsistent between Microsoft and CommVault.
First, I needed to go into Microsoft Entra ID. Two years ago this was named Azure Active Directory so right from the start there are struggles accessing the correct screens - thanks Microsoft. Once there, I generated new secret keys for the apps used by CommVault to do OneDrive backups.
Next, I connected to Command Center and navigated to Protect > Office 365 > OneDrive_V2 > Configuration (tab) > OneDrive Connection Settings (tile). After clicking Add Azure app, I selected Custom configuration and entered the Value from Azure into the Application ID field, and entered the Secret Key from Azure into the Application Secret field. This is the attempt that gave the ErrorCode: AADSTS700016 error. Further digging found the CvCloudBkup (not 100% certain on that name) log file contained the following.
Failed with exception [AADSTS700016: Application with identifier '<Azure GUID>' was not found in the directory '<Corporate Azure Account>'].
My second attempt was to return to add an Azure app but this time enter the Application (client) ID from Azure into the Application ID field and entered the Secret Key from Azure into the Application Secret field. This got rid of the ‘Application not found in directory’ message but still failed to connect to Azure to allow backups.
By this point I’m looking at trying every possible permutation and combination of values from Azure into CommVault to see if I can find one that works. Once again, I return to Command Center and try to add an Azure app but this time enter the Application (client) ID from Azure into the Application ID field and entered the Value from Azure into the Application Secret field. This final attempt was successful and my OneDrive backups are running once again.
Thank you @Ponte_Vedra for the reply. I don’t understand what your reply references and it doesn’t appear to be applicable to my problem but I appreciate the effort.
Ken