Do you have any virus or malware software? Often they can get in the way of running programs downloaded from the internet. Assuming you trust the game, you can try temporarily disabling it.
You can also try using our app, https://itch.io/app. It handles many of the common issues that people have installing and running games from their browser.
If all else fails, the game could actually be broken. In that case you'll have to get in touch with the developer to get support.
Hope that helps