It sounds like itch.io is just experiencing heavy weekend traffic. Mine was working perfectly yesterday, but today it's taking a lot longer to boot up. Your best bet right now is to just hold on the page a little longer than usual. Depending on your internet speed, it should eventually load once it connects to their servers.
Oh, I should also mention: The web version is actually a bit outdated right now. The game got so big that it hit itch.io's maximum file size limit for browser games. If you want the newest update and a smoother experience, definitely grab the PC or Android downloads instead.