How did you subscribe to (and pay for) Shudder?
- Directly with Shudder - Install the Shudder app on your Roku and log into it with the credentials (email and password) you established with Shudder. You should be able to do this on any and all platforms supported by the channel.
- Through Roku - your subscription is with Roku, not Shudder, and you typically would access this through The Roku Channel. Roku should give you access directly with no further need of credential entry.
- Through some other third party (Amazon, Hulu, whatever) - you would typically need to view this on that third party's platform.
Edited to add:
But having said all this, when reinstalling the channel:
After removing the channel, but BEFORE reinstalling it, did you RESTART** your Roku to clear its memory cache? Without the restart you may not get a clean reinstall. This is not a cure-all but at least it will assure you of having an uncorrupted copy of the current channel app.
Depending on your Roku model number you'll find the "System restart" option under either "Settings > System > Power" or under "Settings > System". If you don't have sufficient control to use the menus, or if it is just more convenient, you can also restart by pulling the power plug for a short while, then plugging it back in.
**On a Roku TV with "Fast TV Start" enabled, turning the TV off/on only puts you in/out of a low power standby state, it does NOT give you a complete restart. Use the methods above.