Why do I see boxes when I try to view subtitles in a language

If you do not have the font set for a particular language installed on your computer, you will not be able to view that language. For example, if you choose Bengali and do not have Bengali fonts, you will see boxes instead of the correct subtitles.

To install language fonts you can Google the language and can download most font sets. Once these are installed in your computer, you will be able to view, transcribe and subtitle in that language.