Riot has pushed a patch this morning (GMT) to PBE, temporarily removing all of the 3.10 content which was released Yesterday. The patch contains fixes for some of the bugs contained in the 3.9 release and once stable we are expected to have all the 3.10 content returned!
BrightEyz official statement from the forums:
Summoners, we have temporarily disabled new content to support testing out current live issues. If you experience any bug splats or unusual issues with this build please let us know. Thanks for your help all!
We'll keep you posted!