Hey! This seems like it could either be an issue on Opera's end or on Itch.io's end. Downloads are working fine on our end. Other people might be having issues with downloading this game and others potentially, so we'll keep an eye out for that.
I'd maybe try to restart Opera and try again. If that doesn't work, maybe even restart your PC and try again. If all else fails, just wait a little bit before you try downloading again. It might just be an issue on Itch.io's end.
Let us know if you have any other issues! 😁