Hi @Godhwani, Naina ,
Thanks for reaching out.
identifierUris in the manifest is the Application ID URI which is used to uniquely identify the scopes of your custom api and set while exposing the scopes to another application and hence that entry has to be globally unique. You can either use the default value provided, which is in the form api://<application-client-id> or specify a more readable URI like https://contoso.com/api.
Switching an app registration from single- to multi-tenant can sometimes fail due to Application ID URI (App ID URI) name collisions.
It would always recommend a fresh setup for the app registration, if that is a possibility on your end and set App Id URI which always generates unique App ID URI globally in case of multi-tenant applications or verified customer owned domain.
Hope this will help.
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