I would try the following steps in this order.
1. Uninstall the TCN app from your Roku device.
2. Reboot your Roku device.
3. Go to TCN website and select "Forgot password". From the FAQS page, this should send you a link at your email. https://tuckercarlson.com/faq. (Do not change your password from within your account info, use that "forgot password" procedure).
4. Test the new password on the TCN website and make sure it works.
5. Reinstall the TCN app onto your Roku device and perform another Roku device reboot.
6. Launch TCN on Roku and try to Sign-in from the upper right icon using the TCN credentials.
7. If the above step didn't work, try using the "Subscribe" option from the upper menu instead (next to "browse") and select Cancel. Then scroll all the way down and select "Already a User" Then select "Use different email". Put your TCN credentials here and see if that helps.
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There seems to be multiple areas on the app to sign in. (On the main screen, there is a sign-in" next to the Read More and then there is the "account profile/icon" in upper right, and then also a sign-in option under the Subscribe option.) Could be that just one of these is broken and need to try one of the others.
If all else fails, I would reach out to support@TCNetwork.com from their FAQS page and see if they have some suggestions as well. It is either user error or something in their app may not be working properly causing this login error.
@AvsGunnar Thank you for the detailed response. I noticed that the roku text entry screen had what looked like the same special character in 2 locations on the screen. They looked the same but once i chose the other one my password worked.
Thank you. The process above works. FYI, that was painful!