The reason why the message not showing in Web or Windows app maybe the message not send from your SIM card. If it send from SMS app it will not appear in the desktop SMS feature.
Hi, thank you for getting back to me. I still don't understand why ALL other SMS messages appear and are fine. I can see them on phone, WebUI and Windows app; I can reply to them and all message conversations update. Again, this is just other T-Mobile users, (not including sending and receiving to myself).
Thanks,
Chris