This was surprisingly difficult. I tried to add a coupon for $25 off, and it wouldn’t work. I eventually had to do it by percentage, and that worked for some reason.
It suddenly stopped working right before we were going to watch a new episode of The White Lotus
It turns out that Roku auto-updates to the latest client (not sure if I can even disable this), and the new client was not backwards compatible with whatever server version I installed six months ago