Could you give me more details? When did this happen? Were you trying to watch one of the animations? When did you open the game? If so, try closing and reopening the game.
Make sure the version you downloaded is the smartphone version. If you're running it in the RPG Maker MZ emulator, try other emulator options as well. If you're on a computer, you should download the Mac or Windows version; just unzip it and open the .exe file
If you can read the game’s initial message before the error appears, follow the instructions in the message: download a video codec for your device—the most popular one is the K-Lite Codec Pack—and install it so that the animations will appear in your game.