I submit this review in addition to my previous review 3rd June 2016.
dabruna says "Where is button?" (6th June 2016)
There is no button, as I said in my previous review the subtitles that are available appear in RED showing language options, this is to be seen just below the Youtube Subscribe option.
I have now tried this on an old Windows 7 laptop to make sure it is also compatible as well as my Windows 8.1
It works perfectly.
I have Firefox 46.0.1