A mobile-versus-web report should compare the same conversation action at roughly the same time: send, receive, history load, or notification. Note whether both devices use the same network and account. A successful mobile send on cellular data does not by itself prove the web app is broken on Wi-Fi.
Use a non-sensitive test if needed, and do not post conversation text or contact details. Record the app and browser versions and any safe error code. Check whether the recipient actually receives the message, not only whether the local interface marks it sent. The difference may be in client state, network route, or a partial service incident; report evidence without naming a cause prematurely.
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