I saw a post above about removing an affected device via web login.
That seems to have worked for me. I was only able to see registered devices using my computer (login via mobile device doesn’t show it, or I couldn’t figure out how to get to it).
I expected to find a lot of devices like my new phone, my old phone, a couple of connected TVs and so forth. But the device list only showed my two Roku-connected TVs. I removed the one that was giving problems, logged out, and went back to my Roku-connected TV.
The Cineplex app was still there, and when I tried to login it was successful.
Thanks Moody2U - your solution worked for me too. I know I had tried this before, so maybe they fixed the problem.
I found that credit card on file had expired, possibly causing account to be suspended, after updating information, deleted cineplex and reinstalled, this corrected the issue.