Thanks for your first post in the Roku Community!
We can certainly understand your concern that you are unable to find the FlixFling channel on your Roku device.
Please be aware that If you can no longer find the channel in the Roku Channel Store or the access code no longer works, the channel may no longer be available on the Roku platform.
Note: If you subscribed to or purchased content on a channel that is no longer available on your Roku device, you can contact the content provider for more information.
For full information on this, you can take a look at this Support link page: Why is a channel no longer available on my Roku® streaming device? | Official Roku Support
Please let us know if there's anything else we can help you with.