Resolved
The Outlook integration is stable again for users using cloud accounts. Accounts using hosting on-premise with Microsoft Exchange Server are not able to use the Outlook integration currently.
Investigating
We have encountered problems with flows that use the Outlook app. Sometimes, during the testing of the flow, it fails, and in other cases, the flow execution is incomplete. This means that after the flow has been published, the operations used by the flow are not completed until the end. We are currently investigating the issue and will provide more information as soon as possible.
Flows with other integrations don't seem to be affected by this issue.