@Nitish Sharma Thanks for asking question! Could you please check your connection string format-
The format of the connection string changes based on whether the indexer is using delegated API permissions or application API permissions
Delegated API permissions connection string format
SharePointOnlineEndpoint=[SharePoint site url];ApplicationId=[Azure AD App ID];TenantId=[SharePoint site tenant id]
Application API permissions connection string format
SharePointOnlineEndpoint=[SharePoint site url];ApplicationId=[Azure AD App ID];ApplicationSecret=[Azure AD App client secret];TenantId=[SharePoint site tenant id]
Note
If the SharePoint site is in the same tenant as the search service and system-assigned managed identity is enabled, TenantId
doesn't have to be included in the connection string.
If the SharePoint site is in a different tenant from the search service, TenantId
must be included.
Let us know.