Syncing an Outlook work or school email is dependent on your organization's server settings. An organization can enable both or just 1 of the authentication methods that exist within Outlook: Office 365 (Modern / OAuth) or Exchange (Basic).
If your organization has both enabled, you might be prompted to choose an "email provider" as shown below:
In general, modern Office 365 authentication is preferred by email administrators as it is more secure.
Note: Office 365 sometimes requires administrator approval. If that is the case, you might see the following message:
If you see the "Need admin approval" message, we suggest you try syncing your calendar with Exchange. If your organization has this enabled, your calendar should sync. However, if Basic authentication is disabled, you might see the following message:
If you find neither process is working for you, we suggest you reach out to your email administrators. This is the best way to know whether to opt for Modern or Basic authentication!