Getting error: Field not permitted in query

Hello,

In my custom app I have a DocType My Route Card in which I have set a field qty_per_kg to Fetch from my_work_order_num.qty_per_kg. Here my_work_order_num is field in My Route Card.

But I keep getting this error on the remote server where I have deployed my Custom App.

How to solve this error?

TIA

Yogi Yang