You can try any of the following solutions:
- Download the game again.
- Run the game from the .zip (without extracting)
- Run the game after extracting the .zip (all 5 files must be together in the same folder)
- Install the game from the itchio app, or from the browser if you didn't already.
- You can find some tutorials on youtube on how to fix the "missing UnityPlayer.dll" problem.
Please tell me if you manage to solve the problem.