FREE - In Google Play
FREE - in Win Phone Store
Ps. it worked fine yesterday.
Two things to try:
1. Toggle wifi off and on (or on and off).
2. Open your phone browser and log in to chess.com then try to return to the app.
I've had to do do one or the other in the past to resolve. Note that in both instances, I killed the app first.
Let me know if either of the above help.