[Admob] CPM Imps problem

Dear all,

Nice to meet you. I am new to here. I have a question about Admob.
From 2014/1/22 to 2014/1/27, i got average 2500 CPM Imps each day.
However, @2014/1/28, it suddenly dropped to 0 and never come back. :frowning:
what happens? Did I do something wrong?

Thank you for your help!




Are you using multi ad services or admob mediation services?