I don’t know if the problem has been eliminated in UNA 13 RC, but in UNA 12 the latest UNA messenger update there is no camera change button and you can’t record video from the laptop to the messenger.
Can you please send me details of your site via PM, I will check.
You can watch it on the website UNA.io in the messenger. The same.
I've just checked it in chrome and it is working fine for me. Could you please specify which OS (Windows, MAC, Andriod, IOS) and which browser do you use?