I recently bought a T650 soundbar and no matter what troubleshooting steps I follow, it just won't connect to the SmartThings app, which I found very frustrating because I bought the soundbar specifically to connect it to my Alexa and you can't really do that beyond a direct Bluetooth connection which is pretty much useless if you have it connected it to your TV.
I've unplugged and it plugged it back in, did a manual firmware update via a USB stick (!! -- what am I? A caveman?!), reset my router, changed the wifi-name, tried different wifi frequencies, disconnected the soundbar from the tv, etc... And nothing! The app either doesn't find the soundbar at all or it gets to 37%, gets stuck there and it fails. Why I found even more infuriating is that I contacted Samsung and all they did after they asked me for all this info and screenshots is send me a PDF of the manual. Seriously, WTF Samsung?
