Google has confirmed about a bug in Google AdWords Help forum thread. This bug doesn’t allow some advertisers to see why some of their ads are not approved. In other words, when an ad is not approved, it does not show why it is disapproved, usually it does tell the advertiser why.
Below you can see a typical ad disapproval bubble showing why the ad was not approved/disapproved:
In some cases, the advertisers are not seeing anything except a disapproval notice with no reason on why the ad was disapproved.
Cassie from Google said:
I’ve just confirmed that some other advertisers are experiencing this as well. The engineering team is currently working on a fix.
In the meantime, can you please get in touch directly with AdWords Support? You can reach them via your country’s phone number on this page. We don’t have access to your account from this forum, but they will be able to look at the ad for you and escalate this.