The error message "GetReaderModel API error: "", Response HTTP code: 0" indicates that there may be issues with the Immersive Reader service in OneNote Desktop. Since you've already tried reinstalling the app, testing on different operating systems, and using various networks without success, the issue might be related to service availability or configuration settings within your tenant.
Here are a few suggestions to troubleshoot further:
- Check Service Status: Verify if there are any ongoing issues with the Immersive Reader service on the Microsoft 365 Service Health Dashboard.
- Permissions: Ensure that the users in your tenant have the necessary permissions to access the Immersive Reader feature.
- Tenant Configuration: Review the tenant settings to see if there are any restrictions or policies that might affect the Immersive Reader functionality.
- Contact Support: If the issue persists, consider reaching out to Microsoft Support for assistance, as they may have more insight into tenant-specific issues.
Since the web version and Immersive Reader in Word are working, this suggests that the issue is specific to the OneNote Desktop application.