Error is coming while validating the MS Outlook Calendar in Lower environment

Summary:

While trying to validate the Microsoft Outlook calendar integration in one of our lower environments, we are getting an error "User not found".

Content (please ensure you mask any confidential information):

We have enabled the Microsoft Outlook calendar integration in our lower pods and in Production. But when we are trying to validate the MS Outlook Calendar in Lower environment, we are getting an error ""User not found". However, we are using proper credentials for the Organizer email address field while validating in the Lower pods. Still we are getting this error. However, this is working fine in Production.