I had problems with this or a similar issue last year. CC quit working on some channels. After seeing no answers here solved the problem I did more internet searching and saw a suggestion from someone about experimenting with the Picture/Display modes. I don't remember if it ended up coming from these forums or somewhere else, but it did solve my problem.
On our Samsung TV remote I pushed Menu and went to Picture then chose Picture Mode. If it was on Dynamic I changed it to Standard, but eventually ended back up with the Dynamic option. I think Dynamic is recommended, but switching it off I think did something.
On the Roku box I went to Accessibility, then Captions mode and made sure it was set at On always.
On the Roku box I also went to Display type and experimented with the different settings there. Recommended is Automatic 1080p, but I changed it but eventually ended back on Automatic 1080p.
I then did a reset on the Roku box. Perhaps did a reset by unplugging the box for 30 seconds or from Settings, System, System restart. Or I did both.
I made notes as I made changes to these modes/options so I could get back to these settings and change them again if I needed to.
Why making changes to Picture/Display solved the problem, I do not know, but it did. The person that made these suggestions had a better understanding, but I do know my problem went away after playing with both the TV settings and the Roku box settings.
I did delete an app for one of the channels that quit working and reinstalled it. You can then go to the app and hit the * button and Check for Updates, but that did nothing for me.
You are also told to contact the app channel creators directly, but if it worked one day and quit the next, it's just not an app creator's problem. Why the Roku seems to get a bug now and then is odd and for me it was very frustrating, as you are on your own.
Good luck. I had to spend a lot of time searching the net to find this solution. The one answer you have so far is the same answer I came across here on the Community and it was pretty much useless then.