First check that the file opens on your device and that you have a stable connection. Read any message about the file type, file size or model support.
Try selecting the file again through the attachment option. If the issue affects only one file, mention that when reporting it; if it affects every file, include that detail too.
Send support the file type, size, selected model and error message. You do not need to send a document containing private information just to describe the problem.