Shopify ERPNext Sales Order Hook Not working

Hi ,
I am trying out the Shopify Integration with ERPNext. Sales Order from shopify is automatically created in ERPNext.

I wanted to hook to the doc event 'validate’ for the orders coming from shopify.
This is not working. However for the Sales order created using ERPNext UI, validate hook is working.

Also i tried changing the shopify connector python file. However the code changes are not reflected. Do we need to build something after making changes to python file?

How to debug this? I guess this SO creation happens as a background job. Is that correct? How to debug the background scheduler jobs?