As of December 9, 2021, the NFB (National Film Board of Canada) app will no longer be available through Optik TV as NFB has decided to turn down the capability on the TELUS TV platform. This was a free app included in your Optik TV subscription so there is no impact to your monthly bill. No action is required from you.
Or it's possible NFB is focusing on only certain platforms now. Their website seems to indicate they are only offering on demand on Roku, Apple TV, FireTV, and AndroidTV. The Telus set top boxes (with the excpetion of the old AndroidTV based PikTV box) run on a different software platform that I would guess is less common these days. NFB didn't appear to make a press release about the changes to on demand.