Sending, receiving, and organizing email in Outlook on the web for business
Based on your description, this issue appears to be related to Microsoft's ongoing service incident (Incident ID: MO1550821), which is affecting connectivity to multiple Microsoft 365 services, including Exchange Online, Microsoft Teams, and SharePoint Online.
Microsoft is still working to restore the affected services, and a full restoration time has not yet been confirmed. If you are a Microsoft 365 administrator, you can check the Service Health dashboard in the Microsoft 365 Admin Center for the latest updates on the incident and its recovery progress.
If you're an end user without admin permissions, kindly reach out to your organization's IT administrator for assistance. If you're unsure who your Microsoft 365 administrator is, you can find guidance here: How can I find my Microsoft 365 admin? - Microsoft Support