Has your traffic already reached 5,000/day? Wow that's great, especially since new websites usually get stuck in Google's sandbox.
ExoClick is known for being strict with their policies. If your CTR drops below 0.01%, there's a high chance you'll get banned. Or even if one of your videos accidentally includes content they prohibit.
I usually contact them directly whenever one of my zones suddenly gets rejected.
But if you're thinking about switching, you might want to try HilltopAds. In my case, they pay much better for banners compared to ExoClick. Though to be fair, they're also pretty strict.
Or maybe you could visit the AdSpyglass website and look for the top-performing ad networks based on your GEO.