This happens repeatedly to me too. It sits there frozen, with the logo, and I have to go back. But when I uninstall the app, re-install cineplex, and log in - then it works. No, I did not need updates; there hasn't been an update to the app in a long time.
The real problem is - WHY DOES THIS KEEP HAPPENING? It works once, a single time after logging in. Then when the Roku TV is turned off and I start again some time - the cineplex app freezes again if I try to load it a second time. Now I have to do the cumbersome process of deleting the app, reinstalling, and logging in again. This doesn't happen to Disney+, or Netflix, or Amazon Prime, or literally any other app - it's only Cineplex that doesn't start a 2nd time after install.
I find it hard to believe a bug of this severity has been overlooked for so long. I'd be suspicious that Roku is deliberately ignoring this because they have their own movie/tv show rental system configured, and it's convenient to just have a competitor app sabotaged like this. This is the 12-15th time I've had to reinstall the cineplex app to get it to work over the last 2+ years, and can't believe this hasn't been found before or addressed yet.