All you have to do is go to playstore, download the above app and repeat the steps that you have doing all these while. Don't forget to update your tv to the new update.
This is not OnePlus technical team. I am a customer. I called Amazon and OnePlus customer care. Both didn't know this. I pity the knowledge of the technical team. However, I found this by luck. Glad. Hope it helps. Do let me know by commenting. Peace.
Nice of you to share the info.
But this was already provided in the Official post about how to make Alexa work with the OnePlus TV. If you would have done a simple search, things would have been simpler for you.
Next time make sure to search before posting. Much of the information is made availble in detail in the forums.
[Challenge] Spookify Your OnePlus Photos
by Bouncer71, 2020-10-29