In order to try to help you, I will need to know more details. Are your games connected to a King or a Facebook account? Which platform are you playing on? The last but not least, check if your connection works properly and if your game is up to date. You can also try the steps provided by @Mimckellips and see if it helps.
I play on android connected to Facebook. Actually it's not so much for me, maybe the person who used to send me lives is sick or something, but it's more because I hear so many complain in the Facebook forum about it that I thought it was an issue with me and others as well. Apparently it doesn't seem to be an issue if it still works for many other people. Thanks.