I have a feeling that everyone who is having this issue is playing on king.com. It is no longer supported nor do I think the studio will try to find a fix since they no longer use Flash for this game. My suggestion to you is to try playing either through Facebook via their website or if you can access it from a mobile device because that is using the HTML which is the current version of the game. You can also access the game via Windows 10 and you can log in with the Kingdom account.
I am hoping that it works. Sometimes it's just an easy fix so that is why they suggest trying the troubleshooting first. Just do NOT uninstall the game as you will lose your lives and boosters. I will keep my fingers crossed for you. Also are you playing through Facebook or the Kingdom? If it is Facebook you can always uninstall the Facebook app and reinstall it again. I think there was a Facebook update a couple of days ago.
The Kingdom is the same as king.com. So depending where you are opening the game when it says to login just use your existing email address and password that you would have used for king.com. I only play the games through the Kingdom.