M365 Outlook (Known Issues) Importing ICS Files Error
There is a known issue with importing ics files within the Outlook Web App and Outlook desktop users for both Mac and Windows.
Message displayed:
The events couldn't be imported. Please try again later. Error message: An internal server error occurred. The operation failed.
Troubleshooting
Open the .ICS file in a text editor like Notepad for Windows or TextEdit for Mac, then search for METHOD: REQUEST and change that to METHOD:PUBLISH, save the changes and proceed to import the file as you were doing it.
