itch.io

If you bought the game no, you already paid.

What device or platform? 
Steam/Itch.io - You should be able to see a "Update" button when opening Steam/Itch.io
Android/Apple - You should be able to open your play store and update the game there

Hope that helps

You may need to restart the device or in the game its self change your server to another country than change it back to the servers you were using(Change from Asia to EU or NA than change it back). Hope that helps.

Did you try opening the file and the context inside? If that doesn't work you may need to delete that file and redownload. Hopefully that helps.