Until recently I also never had problems boosting or promoting my posts, but suddenly ads got disapproved, saying: because it's gambling related, the ad needs to be pre-approved by Facebook.
Ok, so I've sent them a message asking how to apply for approval. They answered that I needed pre-approval..... I asked again, how do I apply? Once again the answer was: your ads need pre-approval....duhhhhhh very helpful, NOT!
It reminded me of similar conversations in the early days with AdWords. Saying you did something wrong, but not saying what exactly is wrong and how to correct it. Very annoying.
I continued boosting my ads and got more and more disapprovals. Yet still no answer to my question how to apply. Finally I received a message saying that I breached their T&C's too often and that my advertising account has been disabled, without any possibility to get it re-actived again. Morons!