First and foremost, please ensure that you have the latest version of Yahoo Mail application on your phone to avoid any unnecessary issues with your email documents or attachments. If you are using the browser instead, please ensure compatibility between your web browser and Yahoo Mail and make sure that it is updated. If you use an incompatible or outdated browser, it can lead to problems like Yahoo mail attachment not working. Next, you can delete or clear the browser's cache to troubleshoot this problem. If you have Yahoo mail on your Android device, please remove Yahoo’s mail mobile application’s cache. The extra or additional solution for this problem is to force stop the application altogether and re-open it; this will enable re-establishing the application conflicts. Moreover, you can delete the account from the Yahoo mail application and add it back if the problem is with one account.