I'm having the same issue. I emailed the developer and got sent here where apparently there is no fix. How disappointing. I wonder how long I'll wait until I uninstall. Happening on my Galaxy s5. Based on the previous posts, I'll try my Galaxy Tab.
Same thing here on my iPhone! I've emailed King and have gotten nothing back! I hope they fix it soon! I can see my friends progress ahead of me but my levels are all grayed out!