Updating Qty Available at Source in Production Plan or Work Order

So I have created a production plan and generated a material request based on the plan.
Everything goes smoothly and functions as required, but once I receive the material at the source warehouse, the field Qty Available at Source in the work order does not get updated. It keeps showing the qty as 0, whereas I have received the material.
In my material request list, I can also see the material request as completed.

Any ideas how to solve this?