Nethergate isn't activating

Hi, Since the new update and the hotfix to bring diamond spawning back, I have found that when I have built a nether gate, it has refused to activate. I know I'm creating the structure correctly as I have used your own gamepedia page to double check that nothing had changed to it. This is a bit of an off putting dilemma as many people will now be unable to go into the nether and thus the End until this is fixed. 

 

Many thanks

Jade