Using Outlook for Android for personal email and calendar management
Hello
Since Yahoo works on your laptops, this is likely an authorization problem between Yahoo and Outlook for Android.
Please open Yahoo Account Security in a browser and remove the existing Microsoft Outlook connection if listed. Then go to Android Settings > Apps > Outlook > Storage > Clear data, restart the phone, and add the account again using the Yahoo sign-in option rather than manual IMAP.
If it is still empty, please tell me your Android version, Outlook app version, and whether the Yahoo folders appear in Outlook.
Best regards,
Tao Li