I’m not sure if the restriction is on count.json, but for order look ups, we are restricted to the last 60 days (i think) worth of orders.
As of June 6th, 2018, only the last 60 days’ worth of orders from a store will be accessible from the Order resource by default. If you want to access older orders, then you need to request access to all orders. If your app is granted access, then you can add the read_all_orders scope to your app along with read_orders or write_orders. Private apps are not affected by this change and are automatically granted the scope.
There is a time restriction unless if you have the elevated permission scope to see all orders. Also a culprit is the status parameter. By default it is set to ‘open’. If you want to see all orders regardless of status, try status=any as a parameter.