I have a new Q990F installed and it is working well with the exception of Alexa… I installed Smart Things on my Samsung S25+ and the sound bar is recognised, so I can do all the usual things Device Control things.
However when I go to Service and click Alexa Settings, then Amazon Alexa and then Sign in it says “Loading…” and after ~20 seconds nothing… 
any ideas please? Thanks, Peter
I may need to be corrected on this but I think somebody told me that Alexa on sound bars and TVs cannot link to SmartThings. I definitely could be wrong. I have a V3 and V4 Echo linked to SmartThings.
I just removed my soundbar as it was glitching everything since I installed Alexa. It was a cheaply soundbar so I just removed it. All working perfectly now.
Hi I am also facing the same issue ..have you guys found any solution
I think it’s a big glitch..I found some unique device id for q990f soundbar..chatgpt suggest that firmware is from Kuwait and that it’s got blocked
I got the solution it’s resolved for me
Could you let us know what worked for you please?
Some progress, disconnected Alexa from my SmartThings Apps and re-authorised. Now SmartThings can see my Q990F and I can turn it off-on from the App, including through Google Home and Alexa.
However the Q990F is still not recognising voice commands. Spoke to someone from Samsung and they did not sound too surprised - waiting for a call back again to do more investigation.
Regards, Peter
same here. same soundbar model. can’t get the sign in to work. it says “loading” and gives up in 20 second.
From memory If you disconnect Amazon Alexa from the SmartThings App and then reconnect/re-authorised in the Amazon Alexa in the Smart Things App you can then add the service in the Q-Series App and it does not hang for 20 seconds. However the speaker still does not take Alexa commands through the microphone. I am chasing Samsung…
I’ve tried that a couple of times. Disconnected the apps, re-installed them, re-authorized, re-set the soundbar, re-added it. Nothing worked.
Nightmare:-( When I get to talk to Samsung I’ll post the answer here, Peter
Happy New Year! Great news here - Samsung just released SmartThings app update and the Alexa sign-in now works like a charm!
Spoke to Samsung at length and the outcome is… While the Q990F can be controlled by the Alexa App when it is connected to a PC via HDMI it does NOT accept voice commands - by design! Shame really, it is a great piece of kit 
beside this… Peter