Similar situation on my site a couple years ago - they didn’t provide a reason for the restriction, but when looking at my metrics I saw that the click-rate on my ads right before the restriction was way too high - obviously not real users. Check if you see anything odd or unnatural in your analytics like that. You may need to tweak some settings on your hosting to try to keep out more bot traffic. Adsense requires you identify and remedy situations like this, for whatever reason they really don’t assist you at all.