Around 7:30 p.m. Eastern Time today, I experienced something like this when I went to play Rising World. When I clicked on the Play button in Steam, I was warned of a syncing issue between what I had stored online and what I had on my computer. I said to go ahead anyways, and I couldn't get further than the title page. In my case, a message that I don't recall popped up below the JIW logo on the title page. I force quit to notice a message at the bottom of the Steam front-end that stated "no connection," even though my Internet connection was running fine. I went to play a different game instead.
When I read your message a few minutes ago, I decided to test the game once more and everything was running fine. There wasn't even a "no connection" or a syncing message waiting for me. When we rely on online services, it's to be expected that sooner or later, these services will experience hiccups.
Have you attempted to play the game since you posted your message?