Have you installed SKSE on your own? That could break the game and cause the message. SKSE is preinstalled in Enderal.
The visuals and audio of bink videos can get stuck. Close the game and open the Enderal Launcher, active or deactivate (depends what is set) the OneTWeak option in the launcher. Now you are able to change between fullscreen and borderless window mode. Do it, save the changes, start the game again and the video should play properly.