Thank you for reporting the error.
Some questions for clarification,
- Did the game still load despite the message?
- Was the game playable but with some features seemingly not work properly?
I built and tested the game on a Windows 10 computer using Google Chrome.
Edit: After doing some digging through the Developer console, I've narrowed it down to a problem on itch.io's end or a problem with Unity (the game engine I'm using) that occurs when playing web builds for Firefox. Switching browsers should fix the issue. Sorry for the inconvenience :(