My captions also stopped working for all channels. They stopped when switching from Brit Box. They are now off for all channels, including Brit Box.
Thanks for reaching out here in the Community!
Make sure that closed captioning (abbreviated CC) is activated on your Roku device. To do this, follow the steps below:
For more information, you can visit this link: How do I enable closed captioning?
Let us know if this works for you.
All the best,