EDIT: Not sure about the other issues your having, but Starz was telling me I had reached the maximum devices allowed and wouldn't let me sign in on my living room TV. Here's what I did to fix that:
Go to starz.com/settings. Make like you forgot your password. Use your Roku email to reset your password. Reset it.
Log into Starz with the new password. Go to settings and look for devices. Delete them all. Why all? If you've ever had to use different browsers on various computers, each browser registers as a separate device. Just delete them all then go back to your Roku device and open the Starz app again. It will ask you to go to starz.com/activate (or something similar). Go there and enter the code from your Roku screen. Done. Back to normal.
