orderBy does not exist 跪求解答

 $posts = Tag::find($tag)->posts ->where('published_at', '<=', Carbon::now()->addHour(8))
           ->orderBy('published_at', 'desc')
        ->paginate('10');

为什么我加了“->orderBy()和->paginate(‘10’);”

就会报错Method Illuminate\Database\Eloquent\Collection::orderBy does not exist.

如果不加“->orderBy()和->paginate(‘10’);” 就不会报错

看了文档也是这样写的，新手跪求大哥指导。