Captions on Twitch have now outgrown any possibility of us keeping track of all those who use them. We recommend the following.
Place a closed caption tag on your stream
Information on how this done can be seen here. https://help.twitch.tv/s/article/guide-to-tags?language=en_US
Please make sure that if you have the tag present you have the captions active.
Titles including CC or OC
Another option would be a title with CC aka closed captions or OC open captions.