troyeh49, the standalone Starz app and "Starz on RokuChannel" have different and mutually exclusive subscriptions. It sounds like you have a subscription for the standalone app paid through Roku. I don't know if it will work, but can you try the "Forgot password" option on the Starz website? https://www.starz.com/us/en/login
For the email address, use the one associated with your Roku account that you can see displayed under Settings->System->About. Maybe if you can log into their website you can see what's going on.
Another thing to check is the devices linked to your Roku account that you can see at https://my.roku.com. Remove any devices that you don't recognize.
This is one of those cases that reinforces the belief that many of us here have that you should never subscribe to anything through a third party like Roku, Apple, Amazon, etc. They'll probably just point the finger at each other.